The chromospheric component of coronal bright points. Coronal and chromospheric responses to magnetic-flux emergence |
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Maria Madjarska Submitted: 2020-12-21 22:35
We investigate the chromospheric counterpart of small-scale coronal loops constituting a coronal bright point (CBP) and its response to a photospheric magnetic-flux increase accompanied by co-temporal CBP heating. We used co-observations from the AIA and HMI/SDO, together with data from the Fast Imaging Solar Spectrograph taken in the Hα and Ca II 8542 lines. We used a new multi-layer spectral inversion technique to derive the temporal variations of the temperature of the Hα loops (HLs). We find that the counterpart of the CBP, as seen at chromospheric temperatures, is composed of a bundle of dark elongated features named in this work Hα loops, which constitute an integral part of the CBP loop magnetic structure. An increase in the photospheric magnetic flux due to flux emergence is accompanied by a rise of the coronal emission of the CBP loops, that is a heating episode. We also observe enhanced chromospheric activity associated with the occurrence of new HLs and mottles. While the coronal emission and magnetic flux increases appear to be co-temporal, the response of the Hα counterpart of the CBP occurs with a small delay of less than 3 min. A sharp temperature increase is found in one of the HLs and in one of the CBP footpoints estimated at 46% and 55% with respect to the pre-event values, also starting with a delay of less than 3~min following the coronal heating episode. The low-lying CBP loop structure remains non-potential for the entire observing period. The magnetic topological analysis of the overlying corona reveals the presence of a coronal null point at the beginning and towards the end of the heating episode. The delay in the response of the chromospheric counterpart of the CBP suggests that the heating may have occurred at coronal heights.
Authors: Maria S. Madjarska, Jongchul Chae, Fernando Moreno-Insertis, Zhenyong Hou, Daniel Nóbrega-Siverio, Hannah Kwak, Klaus Galsgaard, Kyuhyoun Cho
Projects: SDO-AIA,SDO-HMI
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Publication Status: accepted for publication in A&A
Last Modified: 2020-12-22 08:38
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Eruptions from quiet Sun coronal bright points. I. Observations |
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Maria Madjarska Submitted: 2018-08-15 12:35
Eruptions from coronal bright points (CBPs) are investigated in a two part study. The present study aims to explore in full detail the morphological and dynamical evolution of these eruptions in the context of the full lifetime evolution of CBPs. A follow-up study employs data-driven modelling based on a relaxation code to reproduce
the time evolution of the magnetic field of these eruptive CBPs, and provide an insight on the possible causes for destabilisation and
eruption.
Observations of the full lifetime of CBPs in data taken with the AIA on board SDO in four passbands, He II 304 Å, Fe IX/X 171 Å, Fe XII 193 Å, and Fe XVIII 94 Å are investigated for the occurrence of plasma ejections, micro-flaring, mini-filament eruptions and mini coronal mass ejections (mini-CMEs). First and foremost, our study shows that the majority (76%) of quiet Sun CBPs (31 out of 42 CBPs) produce at least one eruption during their lifetime. From 21 eruptions in 11 CBPs, 18 occur in average ~17 hrs after the CBP formation for an average lifetime of the CBPs in AIA 193 Å of ~21 hrs. This time delay in the eruption occurrence coincides in each BP with the convergence and cancellation phase of the CBP bipole evolution during which the CBPs become smaller until they fully disappear. The remaining three happen 4 - 6 hrs after the CBP formation. In sixteen out of 21 eruptions the magnetic convergence and cancellation involve the CBP main bipoles, while in three eruptions one of the BP magnetic fragments and a pre-existing fragment of opposite polarity converge and cancel. In one BP with two eruptions cancellation was not observed. The CBP eruptions involve in most cases the expulsion of chromospheric material either as elongated filamentary structure (mini-filament, MF) or a volume of cool material (cool plasma cloud, CPC), together with the CBP or higher overlying hot loops. Coronal waves were identified during three eruptions. A micro-flaring is observed beneath all erupting MFs/CPCs. It remains uncertain whether the destabilised MF causes the micro-flaring or the destabilisation and eruption of the MF is triggered by reconnection beneath the filament. In most eruptions, the cool erupting plasma obscures partially or fully the micro-flare until the erupting material moves away from the CBP. From 21 eruptions 11 are found to produce mini-CMEs. The dimming regions associated with the CMEs are found to be occupied by both the "dark" cool plasma and areas of weakened coronal emission caused by the depleted plasma density.
The present study demonstrates that the evolution of small-scale loop structures in the quiet Sun determined by their magnetic footpoint motions and/or ambient field topology, evolve into eruptive phase that triggers the ejection of cool and hot plasma
in the corona
Authors: Chauzhou Mou, Maria S. Madjarska, Klaus Galsgaard, and Lidong Xia
Projects: SDO-AIA,SDO-HMI
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Publication Status: in press in A&A
Last Modified: 2018-08-16 10:40
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Helium abundance and speed difference between helium ions and protons in the solar wind from coronal holes, active regions, and quiet Sun |
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Maria Madjarska Submitted: 2018-05-14 05:36
Two main models have been developed to explain the mechanisms of release, heating and acceleration of the nascent solar wind, the wave-turbulence-driven (WTD) models and reconnection-loop-opening (RLO) models, in which the plasma release processes are fundamentally different. Given that the statistical observational properties of helium ions produced in magnetically diverse solar regions could provide valuable information for the solar wind modelling, we examine the statistical properties of the helium abundance (AHe) and the speed difference between helium ions and protons (vαp) for coronal holes (CHs), active regions (ARs) and the quiet Sun (QS). We find bimodal distributions in the space of AHe and vαp/vA (where vA is the local Alfvén speed)for the solar wind as a whole. The CH wind measurements are concentrated at higher AHe and vαp/vA values with a smaller AHe distribution range, while the AR and QS wind is associated with lower AHe and vαp/vA, and a larger AHe distribution range. The magnetic diversity of the source regions and the physical processes related to it are possibly responsible for the different properties of AHe and vαp/vA. The statistical results suggest that the two solar wind generation mechanisms, WTD and RLO, work in parallel in all solar wind source regions. In CH regions WTD plays a major role, whereas the RLO mechanism is more important in AR and QS.
Authors: Fu, Hui, Madjarska, Maria S., Li, Bo, Xia, LiDong, Huang, ZhengHua
Projects: SDO-AIA,SDO-HMI
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Publication Status: in press in MNRS
Last Modified: 2018-05-14 10:46
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Plasma parameters and geometry of cool and warm active region loops |
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Maria Madjarska Submitted: 2017-05-09 16:57
How the solar corona is heated to high temperatures remains an unsolved mystery in solar physics. In the present study we analyse observations of 50 whole active-region loops taken with the Extreme-ultraviolet Imaging Spectrometer (EIS) on board the Hinode satellite. Eleven loops were classified as cool (<1 MK) and 39 as warm (1-2 MK) loops. We study their plasma parameters such as densities, temperatures, filling factors, non-thermal velocities and Doppler velocities. We combine spectroscopic analysis with linear force-free magnetic-field extrapolation to derive the three-dimensional structure and positioning of the loops, their lengths and heights as well as the magnetic field strength along the loops. We use density-sensitive line pairs from Fe XII, Fe XIII, Si X and Mg VII ions to obtain electron densities by taking special care of intensity background-subtraction. The emission-measure loci method is used to obtain the loop temperatures. We find that the loops are nearly isothermal along the line-of-sight. Their filling factors are between 8% and 89%. We also compare the observed parameters with the theoretical RTV scaling law. We find that most of the loops are in an overpressure state relative to the RTV predictions. In a followup study, we will report a heating model of a parallel-cascade-based mechanism and will compare the model parameters with the loop plasma and structural parameters derived here.
Authors: Haixia Xie, Maria S. Madjarska, Bo Li, Zhenghua Huang, Lidong Xia, Thomas Wiegelmann, Hui Fu, Chaozhou Mou
Projects: Hinode/EIS
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Publication Status: ApJ, accepted for publication
Last Modified: 2017-05-10 09:18
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Charge states and FIP bias of the solar wind from coronal holes, active regions, and quiet Sun |
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Maria Madjarska Submitted: 2017-01-27 00:02
Connecting in-situ measured solar-wind plasma properties with typical regions on the Sun can provide an effective constraint and test to various solar wind models. We examine the statistical characteristics of the solar wind with an origin in different types of source regions. We find that the speed distribution of coronal hole (CH) wind is bimodal with the slow wind peaking at ~400 km s-1 and a fast at ~600 km s-1. An anti-correlation between the solar wind speeds and the O7+/O6+ ion ratio remains valid in all three types of solar wind as well during the three studied solar cycle activity phases, i.e.
solar maximum, decline and minimum. The NFe/NO range and its average values all decrease with the increasing solar wind speed in different types of solar wind. The NFe/NO range (0.06-0.40, FIP boas range 1-7) for AR wind is wider than for CH wind (0.06-0.20, FIP boas range 1-3) while the minimum value of NFe/NO (~0.06) does not change with the variation of speed, and it is similar for all source regions. The two-peak distribution of CH wind and the anti-correlation between the speed and O7+/O6+ in all three types of solar wind can be explained qualitatively by both the wave-turbulence-driven (WTD) and reconnection-loop-opening (RLO) models, whereas the distribution features of NFe/NO in different source regions of solar wind can be explained more reasonably by the RLO models.
Authors: Hui Fu, Maria S. Madjarska, LiDong Xia, Bo Li, ZhengHua Huang, Zhipeng Wangguan
Projects: ACE,SoHO-EIT,SoHO-MDI
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Publication Status: accepted for publication in ApJ
Last Modified: 2017-01-31 11:46
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Kinematics and helicity evolution of a loop-like eruptive prominence |
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Maria Madjarska Submitted: 2012-02-13 06:50
Aims. We aim at investigating the morphology, kinematic and helicityevolution of a loop-like prominence during itseruption. Methods. We use multi-instrument observations from AIA/SDO,EUVI/STEREO and LASCO/SoHO. The kinematic,morphological, geometrical, and helicity evolution of a loop-likeeruptive prominence are studied in the context of themagnetic flux rope model of solar prominences. Results. The prominence eruption evolved as a height expanding twistedloop with both legs anchored in the chromo-sphere of a plage area. The eruption process consists of a prominenceactivation, acceleration, and a phase of constantvelocity. The prominence body was composed of left-hand(counter-clockwise) twisted threads around the main promi-nence axis. The twist during the eruption was estimated at 6π (3 turns). The prominence reached a maximum height of 526 Mm before contracting to its primary location and partiallyreformed in the same place two days after the eruption.This ejection, however, triggered a CME seen in LASCO C2. Theprominence was located in the northern periphery ofthe CME magnetic field configuration and, therefore, the backgroundmagnetic field was asymmetric with respect tothe filament position. The physical conditions of the falling plasmablobs were analysed with respect to the prominencekinematics. Conclusions. The same sign of the prominence body twist and writhe, aswell as the amount of twisting above the criticalvalue of 2π after the activation phase indicate that possibly conditions for kinkinstability were present. No signature ofmagnetic reconnection was observed anywhere in the prominence body andits surroundings. The filament/prominencedescent following the eruption and its partial reformation at the sameplace two days later suggest a confined type oferuption. The asymmetric background magnetic field possibly played animportant role in the failed eruption.
Authors: K. Koleva, M.S. Madjarska, P. Duchlev, C. J. Schrijver, J.-C. Vial, E. Buchlin, and M. Dechev
Projects: SDO-AIA,SoHO-LASCO
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Publication Status: accepted for publication in A&A
Last Modified: 2012-02-14 12:12
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Explosive events associated with a surge |
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Maria Madjarska Submitted: 2009-06-10 07:54
The solar atmosphere contains a wide variety of small-scale transient features.
Here, we explore the inter-relation between some of them such as surges,
explosive events and blinkers via simultaneous spectral and imaging data taken
with the TRACE imager, the SUMER, and CDS spectrometers on board SoHO,
and SVST La Palma. The features were observed in spectral lines with formation
temperatures from 10,000 K to 1 MK and with the TRACE Fe ix/x 171 Å
filter. The Hα filtergrams were taken in the wings of the H 6365 A line at
?700 mA and ?350 mA. The alignment of all data both in time and solar XY
shows that SUMER line profiles, which are attributed to explosive events, are
due to a surge phenomenon. The surge?s up- and down-flows which often appear
simultaneously correspond to the blue- and red-shifted emission of the transition
region N V 1238.82 A and O V 629.77 A lines as well as radiance increases of
the C I, S I and S II and Si II chromospheric lines. Some parts of the surge
are also visible in the TRACE 171 Å images which could suggest heating to
coronal temperatures. The surge is triggered, most probably, by one or more
Elerman bombs which are best visible in H ?350 A but were also registered by
TRACE Fe IX/X 171 Å and correspond to a strong radiance increase in the CDS
Mg IX 368.07 A line. With the present study we demonstrate that the division
of small-scale transient events into a number of different subgroups, for instance
explosive events, blinkers, spicules, surges or just brightenings, is ambiguous,
implying that the definition of a feature based only on either spectroscopic or
imaging characteristics as well as insufficient spectral and spatial resolution can
be incomplete.
Authors: M.S. Madjarska, J.G. Doyle & B. de Pontieu
Projects: SoHO-SUMER,TRACE
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Publication Status: ApJ Part I, in press
Last Modified: 2009-06-10 09:19
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