Large-Scale Solar Coronal Structures in Soft X-Rays and Their Relationship to the Magnetic Flux

Benevolenskaya, E. E.; Kosovichev, A. G.; Lemen, J. R.; Scherrer, P. H.; Slater, G. L.

doi:10.1086/341203

Cited by 37 publications

(39 citation statements)

References 8 publications

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“…Similar to active regions, the PEAs move in latitude from shortly before solar minimum until sometime shortly after the following minimum from the higher latitudes towards the solar equator. Some PEA events at higher latitudes seem to coincide with periods when strong pulses of new magnetic flux caused a migration of the following polarity fields in BPRs towards the Sun's poles in agreement with the findings of Benevolenskaya et al (2002). A linear polynomial fit …”

Section: Photospheric Source Regions and Solar Cycle Dependencesupporting

confidence: 85%

The basic characteristics of EUV post-eruptive arcades and their role as tracers of coronal mass ejection source regions

Tripathi

Bothmer

Cremades

2004

A&A

114

109

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Abstract. The Extreme ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO) spacecraft provides unique observations of dynamic processes in the low corona. The EIT 195 Å data taken from 1997 to the end of 2002 were investigated to study the basic physical properties of post-eruptive arcades (PEAs) and their relationship with coronal mass ejections (CMEs) as detected by SOHO/LASCO (Large Angle Spectrometric Coronagraph). Over the investigated time period, 236 PEA events have been identified in total. For each PEA, its EUV lifetime as derived from the emission time at 195 Å, its heliographic position and length, and its corresponding photospheric source region inferred from SOHO/MDI (Michelson Doppler Imager) data has been studied, as well as the variation of these parameters over the investigated phase of solar cycle 23. An almost one to one correspondence is found between EUV PEAs and white-light CMEs. Based on this finding, PEAs can be considered as reliable tracers of CME events even without simultaneous coronagraph observations. A detailed comparison of the white-light, soft X-ray and EUV observation for some of the events shows, that PEAs form in the aftermath of CMEs likely in the course of the magnetic restructurings taking place at the coronal source sites. The average EUV emission life-time for the selected events ranged from 2 to 20 h, with an average of 7 h. The heliographic length of the PEAs was in the range of 2 to 40 degrees, with an average of 15 degrees. The length increased by a factor of 3 to 4 in the latitude range of 20 to 40 degrees in the northern and southern hemispheres, with longer PEAs being observed preferentially at higher latitudes. The PEAs were located mainly in the activity belts in both hemispheres, with the southern hemispheric ones being shifted by about 15 degree in latitude further away from the solar equator during 1997−2002. The decrease in latitude of the PEA positions was 10 to 15 degrees in the northern and southern hemispheres over this period. The axes of the PEAs were overlying magnetic polarity inversion lines when traced back to the MDI synoptic charts of the photospheric field. The magnetic polarities on both sides of the inversion lines agreed with the dominant magnetic pattern expected in cycle 23, i.e. being preferentially positive to the West of the PEA axes in the North and negative in the South. One third (31%) of the PEA events showed reversed polarities. The origin of PEAs is found not just in single bipolar regions (BPRs), but also in between pairs of neighboring BPRs.

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Section: Photospheric Source Regions and Solar Cycle Dependencesupporting

confidence: 85%

The basic characteristics of EUV post-eruptive arcades and their role as tracers of coronal mass ejection source regions

Tripathi

Bothmer

Cremades

2004

A&A

114

109

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“…We think possible to link this lack of correlation between the coronal EUV emission (namely, from the EIT 195 Å channel) and the soft X-ray emission to a specific brightness difference in polar regions detected with spatially resolved solar images. As revealed in aggregates of Carrington maps of the Sun, the polar regions (presumably loop footpoints) are brighter in coronal EUV emission than in soft X-ray (Benevolenskaya et al 2002, Figure 1, mark II) and are connected via giant loops (visible as diffuse structures in soft X-ray) to the following parts of active regions at midlatitude. In between are filaments located at the magnetic neutral lines, with typical "coronal cavities" surrounding them (Benevolenskaya et al 2001).…”

Section: Mechanisms For the Ultra-long-period Oscillationsmentioning

confidence: 98%

Ultra-Long-Period Oscillations in Euv Filaments Near to Eruption: Two-Wavelength Correlation and Seismology

Foullon¹,

Verwichte²,

Nakariakov

2009

ApJ

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We investigate whether or not ultra-long-period oscillations in EUV filaments can be related to their eruption. We report new observations of long-period (∼10-30 hr) oscillatory motions in an apparently quiescent filament, as it crosses the solar disk in a 12 minute cadence SOHO/Extreme-Ultraviolet Imaging Telescope (EIT) 195 Å uninterrupted data set. This data set is chosen to explore characteristics of the filament oscillations depending on its eruptive behavior, which is observed while the filament is still on the disk. The periods are found to increase in a near-stable regime prior to eruption. For the two sequences reported so far, we compare and link the EUV filament oscillations with pulsations in full-disk solar EUV irradiance from SOHO/CELIAS/SEM 304 Å flux measurements. In intervals with stationary periods, we find that the 304 Å pulsations and the 195 Å filament oscillations have similar periodicities, but are phase-shifted by about a quarter of period. The two-wavelength correlation serves to show that, when the filament is the dominant dynamical feature but can no longer be tracked on the disk, the full-disk irradiance may provide a mean to identify the period increase prior to the filament eruption. We use the periods thus obtained to estimate the height increase of filaments' suspending coronal magnetic field lines, based on a magnetohydrodynamic (MHD) wave interpretation of the oscillations. The results are consistent with changes in prominence heights detected off-limb and thus support the seismological tool employed. Other interpretations connected with thermal overstability or MHD piston effect are possible. These theoretical predictions however do not explain the quarter-period shift between the two EUV-wavelength signals. In any case, the detected variations may provide a powerful diagnostic tool for the forecasting of prominence eruptions.

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“…Benevolenskaya et al 2002). The observed lengths of the SRs (Col. 10 in Table 1) ranged from a few degrees up to more than 40…”

Section: Source Regionsmentioning

confidence: 99%

On the three-dimensional configuration of coronal mass ejections

Cremades

Bothmer

2004

A&A

294

261

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Abstract. Coronal mass ejections (CMEs) are a direct consequence of the dynamic nature of the solar atmosphere. They represent fundamental processes in which energy is transferred from the Sun into interplanetary space, including geospace. Their origin, 3D structure and internal magnetic field configuration are to date not well understood. The SOHO spacecraft, launched by the end of 1995, has provided unprecedented data on CMEs since instruments switched on in 1996. From a detailed investigation of the full set of LASCO (Large Angle Spectroscopic Coronagraph) observations from 1996 to the end of 2002, a set of structured CME events has been identified, which exhibits white-light fine structures likely indicative of their internal magnetic field configuration and possible 3D structure. Their source regions in the low corona and photosphere have been inferred by means of complementary analyses of data from the Extreme-Ultraviolet Imaging Telescope (EIT) and Michelson Doppler Imager (MDI) on board SOHO, and ground-based Hα measurements. According to the results of this study, structured CMEs arise in a self-similar manner from pre-existing small scale loop systems, overlying regions of opposite magnetic polarities. From the characteristic pattern of the CMEs' source regions in both solar hemispheres, a generic scheme is presented in which the projected white-light topology of a CME depends primarily on the orientation and position of the source region's neutral line on the solar disk. The paper also provides information about the white-light characteristics of the analysed CMEs, such as angular width and position angle, with respect to their source region properties, such as heliographic location, inclination and length, including the frequency and variation of these parameters over the investigated time period.

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Large-Scale Solar Coronal Structures in Soft X-Rays and Their Relationship to the Magnetic Flux

Cited by 37 publications

References 8 publications

The basic characteristics of EUV post-eruptive arcades and their role as tracers of coronal mass ejection source regions

The basic characteristics of EUV post-eruptive arcades and their role as tracers of coronal mass ejection source regions

Ultra-Long-Period Oscillations in Euv Filaments Near to Eruption: Two-Wavelength Correlation and Seismology

On the three-dimensional configuration of coronal mass ejections

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