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Comparison of the Scaling Properties of EUV Intensity Fluctuations in Coronal Hole and Quiet-Sun RegionsCadavid, Ana CristinaMiralles, Mari PazRomich, KristineDOI: info:10.3847/1538-4357/ab4d4ev. 886143
Cadavid, Ana Cristina, Miralles, Mari Paz, and Romich, Kristine. 2019. "Comparison of the Scaling Properties of EUV Intensity Fluctuations in Coronal Hole and Quiet-Sun Regions." The Astrophysical Journal 886:143.
ID: 154514
Type: article
Authors: Cadavid, Ana Cristina; Miralles, Mari Paz; Romich, Kristine
Abstract: Using detrended fluctuation analysis and rescaled range analysis, we investigate the scaling properties of extreme ultraviolet (EUV) intensity fluctuations of low-latitude coronal holes (CHs) and neighboring quiet-Sun (QS) regions in signals obtained with the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly instrument. Contemporaneous line-of-sight SDO/Helioseismic and Magnetic Imager magnetic fields provide a context for the physical environment. We find that the intensity fluctuations in the time series of EUV images present at each spatial point a scaling symmetry over the range ∼20 minute to ∼1 hr. Thus we are able to calculate a generalized Hurst exponent and produce image maps, not of physical quantities like intensity or temperature, but of a single dynamical parameter that sums up the statistical nature of the intensity fluctuations at each pixel. In QS regions and in CHs with magnetic bipoles, the scaling exponent (1.0 &lt α ≤ 1.5) corresponds to anticorrelated turbulent-like processes. In CHs, and in QS regions primarily associated with (open) magnetic field of dominant polarity, the generalized exponent (0.5 < α < 1) corresponds to positively correlated (persistent) processes. We identify a tendency for α ∼ 1 near CH boundaries and in other regions in which open and closed magnetic fields are in proximity. This is a signature of an underlying 1/f type process that is characteristic for self-organized criticality and shot-noise models.
Density Diagnostics of Coronal Mass Ejection Cores with the Solar Dynamics Observatory/Atmospheric Imaging AssemblyLandi, E.Miralles, Mari PazDOI: info:10.1088/2041-8205/780/1/L7v. 780L7
Landi, E. and Miralles, Mari Paz. 2014. "Density Diagnostics of Coronal Mass Ejection Cores with the Solar Dynamics Observatory/Atmospheric Imaging Assembly." Astrophysical Journal Letters 780:L7.
ID: 118838
Type: article
Authors: Landi, E.; Miralles, Mari Paz
Abstract: In this Letter, we investigate the application of the intensity ratio from pairs of narrow-band images from the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory, the Extreme Ultraviolet (EUV) Imager (EUVI) on board the Sun Earth Connection Coronal and Heliospheric Investigation, and the EUV Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory, to density diagnostics of optically thin plasmas. By inspecting the filtered spectra allowed by each instrument's effective area, we find that ratios between AIA images in the 171 Å and 193 Å channels can be used to determine the plasma electron density at transition region temperatures. This diagnostic potential is due to a pair of O V transitions which dominate the effective spectra of these two channels at temperatures around ≈2.5-3.0 × 105 K. The temperature and electron density ranges where the 171/193 ratio is density sensitive are relevant for the cores of accelerating coronal mass ejections (CMEs) in the inner solar corona. We discuss how AIA series of images can be used for simultaneous temperature and density diagnostics of CME cores.
Prevalence of small-scale jets from the networks of the solar transition region and chromosphereTian, H.DeLuca, Edward E.Cranmer, S. R.De Pontieu, B.Peter, H.Martínez-Sykora, J.Golub, L.McKillop, S.Reeves, Katharine K.Miralles, Mari PazMcCauley, P.Saar, S.Testa, P.Weber, Mark A.Murphy, N.Lemen, J.Title, A.Boerner, P.Hurlburt, N.Tarbell, T. D.Wuelser, J. P.Kleint, L.Kankelborg, C.Jaeggli, S.Carlsson, M.Hansteen, V.McIntosh, S. W.DOI: info:10.1126/science.1255711v. 3461255711
Tian, H., DeLuca, Edward E., Cranmer, S. R., De Pontieu, B., Peter, H., Martínez-Sykora, J., Golub, L., McKillop, S., Reeves, Katharine K., Miralles, Mari Paz, McCauley, P., Saar, S., Testa, P., Weber, Mark A., Murphy, N., Lemen, J., Title, A., Boerner, P., Hurlburt, N., Tarbell, T. D., Wuelser, J. P., Kleint, L., Kankelborg, C., Jaeggli, S., Carlsson, M. et al. 2014. "Prevalence of small-scale jets from the networks of the solar transition region and chromosphere." Science 346:1255711.
ID: 131080
Type: article
Authors: Tian, H.; DeLuca, Edward E.; Cranmer, S. R.; De Pontieu, B.; Peter, H.; Martínez-Sykora, J.; Golub, L.; McKillop, S.; Reeves, Katharine K.; Miralles, Mari Paz; McCauley, P.; Saar, S.; Testa, P.; Weber, Mark A.; Murphy, N.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser, J. P.; Kleint, L.; Kankelborg, C.; Jaeggli, S.; Carlsson, M.; Hansteen, V.; McIntosh, S. W.
Abstract: As the interface between the Sun's photosphere and corona, the chromosphere and transition region play a key role in the formation and acceleration of the solar wind. Observations from the Interface Region Imaging Spectrograph reveal the prevalence of intermittent small-scale jets with speeds of 80 to 250 kilometers per second from the narrow bright network lanes of this interface region. These jets have lifetimes of 20 to 80 seconds and widths of ≤300 kilometers. They originate from small-scale bright regions, often preceded by footpoint brightenings and accompanied by transverse waves with amplitudes of ~20 kilometers per second. Many jets reach temperatures of at least ~105 kelvin and constitute an important element of the transition region structures. They are likely an intermittent but persistent source of mass and energy for the solar wind.
Hot Plasma Associated with a Coronal Mass EjectionLandi, E.Miralles, Mari PazRaymond, John C.Hara, H.DOI: info:10.1088/0004-637X/778/1/29v. 77829
Landi, E., Miralles, Mari Paz, Raymond, John C., and Hara, H. 2013. "Hot Plasma Associated with a Coronal Mass Ejection." The Astrophysical Journal 778:29.
ID: 118216
Type: article
Authors: Landi, E.; Miralles, Mari Paz; Raymond, John C.; Hara, H.
Abstract: We analyze coordinated observations from the EUV Imaging Spectrometer (EIS) and X-Ray Telescope (XRT) on board Hinode of an X-ray Plasma Ejection (XPE) that occurred during the coronal mass ejection (CME) event of 2008 April 9. The XPE was trailing the CME core from behind, following the same trajectory, and could be identified both in EIS and XRT observations. Using the EIS spectrometer, we have determined the XPE plasma parameters, measuring the electron density, thermal distribution, and elemental composition. We have found that the XPE composition and electron density were very similar to those of the pre-event active region plasma. The XPE temperature was higher, and its thermal distribution peaked at around 3 MK also, typical flare lines were absent from EIS spectra, indicating that any XPE component with temperatures in excess of 5 MK was likely either faint or absent. We used XRT data to investigate the presence of hotter plasma components in the XPE that could have gone undetected by EIS and found that-if at all present-these components have small emission measure values and their temperature is in the 8-12.5 MK range. The very hot plasma found in earlier XPE observations obtained by Yohkoh seems to be largely absent in this CME, although plasma ionization timescales may lead to non-equilibrium ionization effects that could make bright lines from ions formed in a 10 MK plasma not detectable by EIS. Our results supersede the XPE findings of Landi et al., who studied the same event with older response functions for the XRT Al-poly filter; the differences in the results stress the importance of using accurate filter response functions.
Post-Coronal Mass Ejection Plasma Observed by HinodeLandi, E.Raymond, John C.Miralles, Mari PazHara, H.DOI: info:10.1088/0004-637X/751/1/21v. 75121
Landi, E., Raymond, John C., Miralles, Mari Paz, and Hara, H. 2012. "Post-Coronal Mass Ejection Plasma Observed by Hinode." The Astrophysical Journal 751:21.
ID: 111710
Type: article
Authors: Landi, E.; Raymond, John C.; Miralles, Mari Paz; Hara, H.
Abstract: In the present work we study the evolution of an active region after the eruption of a coronal mass ejection (CME) using observations from the EIS and XRT instruments on board Hinode. The field of view includes a post-eruption arcade, a current sheet, and a coronal dimming. The goal of this paper is to provide a comprehensive set of measurements for all these aspects of the CME phenomenon made on the same CME event. The main physical properties of the plasma along the line of sight-electron density, thermal structure, plasma composition, size, and, when possible, mass-are measured and monitored with time for the first three hours following the CME event of 2008 April 9. We find that the loop arcade observed by EIS and XRT may not be related to the post-eruption arcade. Post-CME plasma is hotter than the surrounding corona, but its temperature never exceeds 3 MK. Both the electron density and thermal structure do not show significant evolution with time, while we found that the size of the loop arcade in the Hinode plane of the sky decreased with time. The plasma composition is the same in the current sheet, in the loop arcade, and in the ambient plasma, so all these plasmas are likely of coronal origin. No significant plasma flows were detected.
Asymmetric Magnetic Reconnection in Solar Flare and Coronal Mass Ejection Current SheetsMurphy, N. A.Miralles, Mari PazPope, C. L.Raymond, John C.Winter, H. D.Reeves, Katharine K.Seaton, D. B.van Ballegooijen, Adriaan A.Lin, J.DOI: info:10.1088/0004-637X/751/1/56v. 75156
Murphy, N. A., Miralles, Mari Paz, Pope, C. L., Raymond, John C., Winter, H. D., Reeves, Katharine K., Seaton, D. B., van Ballegooijen, Adriaan A., and Lin, J. 2012. "Asymmetric Magnetic Reconnection in Solar Flare and Coronal Mass Ejection Current Sheets." The Astrophysical Journal 751:56.
ID: 111709
Type: article
Authors: Murphy, N. A.; Miralles, Mari Paz; Pope, C. L.; Raymond, John C.; Winter, H. D.; Reeves, Katharine K.; Seaton, D. B.; van Ballegooijen, Adriaan A.; Lin, J.
Abstract: We present two-dimensional resistive magnetohydrodynamic simulations of line-tied asymmetric magnetic reconnection in the context of solar flare and coronal mass ejection current sheets. The reconnection process is made asymmetric along the inflow direction by allowing the initial upstream magnetic field strengths and densities to differ, and along the outflow direction by placing the initial perturbation near a conducting wall boundary that represents the photosphere. When the upstream magnetic fields are asymmetric, the post-flare loop structure is distorted into a characteristic skewed candle flame shape. The simulations can thus be used to provide constraints on the reconnection asymmetry in post-flare loops. More hard X-ray emission is expected to occur at the footpoint on the weak magnetic field side because energetic particles are more likely to escape the magnetic mirror there than at the strong magnetic field footpoint. The footpoint on the weak magnetic field side is predicted to move more quickly because of the requirement in two dimensions that equal amounts of flux must be reconnected from each upstream region. The X-line drifts away from the conducting wall in all simulations with asymmetric outflow and into the strong magnetic field region during most of the simulations with asymmetric inflow. There is net plasma flow across the X-line for both the inflow and outflow directions. The reconnection exhaust directed away from the obstructing wall is significantly faster than the exhaust directed toward it. The asymmetric inflow condition allows net vorticity in the rising outflow plasmoid which would appear as rolling motions about the flux rope axis.
Properties of a Polar Coronal Hole During the Solar Minimum in 2007Hahn, M.Bryans, P.Landi, E.Miralles, Mari PazSavin, D. W.DOI: info:10.1088/0004-637X/725/1/774v. 725774–786
Hahn, M., Bryans, P., Landi, E., Miralles, Mari Paz, and Savin, D. W. 2010. "Properties of a Polar Coronal Hole During the Solar Minimum in 2007." The Astrophysical Journal 725:774– 786.
ID: 98084
Type: article
Authors: Hahn, M.; Bryans, P.; Landi, E.; Miralles, Mari Paz; Savin, D. W.
Abstract: We report measurements of a polar coronal hole during the recent solar minimum using the Extreme Ultraviolet Imaging Spectrometer on Hinode. Five observations are analyzed that span the polar coronal hole from the central meridian to the boundary with the quiet-Sun corona. We study the observations above the solar limb in the height range of 1.03-1.20 R sun. The electron temperature T e and emission measure (EM) are found using a geometric mean emission measure method. The EM derived from the elements Fe, Si, S, and Al are compared in order
Physical Conditions in a Coronal Mass Ejection from Hinode, Stereo, and SOHO ObservationsLandi, E.Raymond, John C.Miralles, Mari PazHara, H.v. 71175–98
Landi, E., Raymond, John C., Miralles, Mari Paz, and Hara, H. 2010. "Physical Conditions in a Coronal Mass Ejection from Hinode, Stereo, and SOHO Observations." The Astrophysical Journal 711:75– 98.
ID: 81932
Type: article
Authors: Landi, E.; Raymond, John C.; Miralles, Mari Paz; Hara, H.
Physical Properties of Cooling Plasma in Quiescent Active Region LoopsLandi, E.Miralles, Mari PazCurdt, W.Hara, H.DOI: info:10.1088/0004-637X/695/1/221v. 695221–237
Landi, E., Miralles, Mari Paz, Curdt, W., and Hara, H. 2009. "Physical Properties of Cooling Plasma in Quiescent Active Region Loops." The Astrophysical Journal 695:221– 237.
ID: 78304
Type: article
Authors: Landi, E.; Miralles, Mari Paz; Curdt, W.; Hara, H.