We report the first detection of metric radio emission from a surge, observed with the Nançay Rad... more We report the first detection of metric radio emission from a surge, observed with the Nançay Radioheliograph (NRH), STEREO, and other instruments. The emission was observed during the late phase of the M9 complex event SOL2010-02-012T11:25:00, described in a previous publication. It was associated with a secondary energy release, also observed in STEREO 304 Å images, and there was no detectable soft X-ray emission. The triangulation of the STEREO images allowed for the identification of the surge with NRH sources near the central meridian. The radio emission of the surge occurred in two phases and consisted of two sources, one located near the base of the surge, apparently at or near the site of energy release, and another in the upper part of the surge; these were best visible in the frequency range of 445.0 to about 300 MHz, whereas a spectral component of a different nature was observed at lower frequencies. Sub-second time variations were detected in both sources during both ph...
We have studied a complex metric radio event that originated in a compact flare, observed with th... more We have studied a complex metric radio event that originated in a compact flare, observed with the ARTEMIS-JLS radiospectrograph on February 12, 2010. The event was associated with a surge observed at 195 and 304 Å and with a coronal mass ejection observed by instruments on board STEREO A and B near the eastern and western limbs respectively. On the disk the event was observed at ten frequencies by the Nançay Radioheliograph (NRH), in Hαby the Catania observatory, in soft X-rays by GOES SXI and Hinode XRT, and in hard X-rays by RHESSI. We combined these data, together with MDI longitudinal magnetograms, to get as complete a picture of the event as possible. Our emphasis is on two type-II bursts that occurred near respective maxima in the GOES light curves. The first, associated with the main peak of the event, showed an impressive fundamental-harmonic structure, while the emission of the second consisted of three well-separated bands with superposed pulsations. Using positional info...
We present observations of a UV event which occurred in a polar coronal hole. They were obtained ... more We present observations of a UV event which occurred in a polar coronal hole. They were obtained by SUMER on SOHO in several chromospheric and transition region spectral lines. Its birth site was about 50 arc sec inside the limb and in a network lane showing a net outflow before its initiation. The event had an extension of about 5 arc sec along the
One of the major discoveries of EIT on SOHO was the observation of large-scale EUV intensity dist... more One of the major discoveries of EIT on SOHO was the observation of large-scale EUV intensity disturbances which travel over significant fractions of the solar disk. These `EUV waves' are associated with CME onsets and can be either an MHD wave triggered by the eruption or the footprints of the associated CME, which currently is a subject of intense debate.
ABSTRACT Coronal mass ejection (CME) cavities seen in white-light coronagraphs expand nearly self... more ABSTRACT Coronal mass ejection (CME) cavities seen in white-light coronagraphs expand nearly self similarly in the outer corona and inner solar wind. Little is known about their initial expansion in the inner corona. A two-phase evolution, consisting of an initial overexpansion up to a heliocentric front height of about 1.5 solar radii, followed by nearly self-similar expansion, was recently discovered in STEREO/SECCHI observations of a fast CME (Patsourakos et al. 2010). The overexpansion is expressed as a decrease of the cavity aspect ratio (center height by radius) by at least a factor of 2 during the rise phase of the main CME acceleration. We present MHD simulations of erupting flux ropes that show the initial overexpansion of a cavity in line with the observed evolution. The contributions of ideal-MHD expansion and of magnetic reconnection to the growth of the flux rope and cavity in the simulations will be quantified to identify the primary cause of the overexpansion. This assesses the diagnostic potential of the overexpansion for the change of flux rope current and the role of magnetic reconnection in the early evolution of CMEs.
ABSTRACT Despite observations of thousands of coronal mass ejections (CMEs), the details of their... more ABSTRACT Despite observations of thousands of coronal mass ejections (CMEs), the details of their formation still elude us. Impulsive CMEs, in particular, originate low in the corona, and form within 10-15 mins while accelerating rapidly. This region of the corona is regularly observed by EUV imagers but the rapid CME evolution requires high cadence and relatively large fields of view. Thanks to the operation of the STEREO and SDO missions, we are currently in a unique position to address the problem of CME formation. The two missions provide almost simultaneous observations from three viewpoints with 3 EUV imagers. The EUV instruments observe in the same (or similar) channels and have highly complimentary cadences and fields of view. In this paper, we discuss a coherent picture of the birth of CMEs based on a study of the first few-minute evolution of several impulsive CMEs. These CMEs seem to first undergo an non-linear expansion followed by a self-similar phase. We discuss the implication for CME initiation models.
ABSTRACT Understanding the first moments in the life-time of Coronal Mass Ejections (CMEs), i.e. ... more ABSTRACT Understanding the first moments in the life-time of Coronal Mass Ejections (CMEs), i.e. their genesis, represents possibly the key to unlock the physical processes responsible for their initiation. After this critical interval, which could last as little as few minutes for the most impulsive events, differences between various CME models become minimal. The recent launch of the SDO mission and the availability of high-quality EUV imaging from AIA in particular, opened a new avenue into CME initiation investigations with its unprecedented image cadence and multi-wavelength simultaneous coverage. We here report on AIA observations of an impulsive CME-flare-EUV wave event which took place during 13 June 2010. All the important dynamics (e.g., rise phase of the flare, impulsive acceleration of the CME) had a duration of only 10 minutes making this event a perfect showcase event for AIA. Taking advantage of the unique aspects of AIA data (12 sec cadence and 7 different EUV channels) we present a detailed analysis of this event which includes: (1) its kinematic behavior (acceleration profile); (2) radial and expansion speeds; (3) relationships between (1) and (2) with the flare energy release; (4) multi-temperature evolution of the early CME. All the above supply new strong constraints for the physics of impulsive CMEs.
We report the first detection of metric radio emission from a surge, observed with the Nançay Rad... more We report the first detection of metric radio emission from a surge, observed with the Nançay Radioheliograph (NRH), STEREO, and other instruments. The emission was observed during the late phase of the M9 complex event SOL2010-02-012T11:25:00, described in a previous publication. It was associated with a secondary energy release, also observed in STEREO 304 Å images, and there was no detectable soft X-ray emission. The triangulation of the STEREO images allowed for the identification of the surge with NRH sources near the central meridian. The radio emission of the surge occurred in two phases and consisted of two sources, one located near the base of the surge, apparently at or near the site of energy release, and another in the upper part of the surge; these were best visible in the frequency range of 445.0 to about 300 MHz, whereas a spectral component of a different nature was observed at lower frequencies. Sub-second time variations were detected in both sources during both ph...
We have studied a complex metric radio event that originated in a compact flare, observed with th... more We have studied a complex metric radio event that originated in a compact flare, observed with the ARTEMIS-JLS radiospectrograph on February 12, 2010. The event was associated with a surge observed at 195 and 304 Å and with a coronal mass ejection observed by instruments on board STEREO A and B near the eastern and western limbs respectively. On the disk the event was observed at ten frequencies by the Nançay Radioheliograph (NRH), in Hαby the Catania observatory, in soft X-rays by GOES SXI and Hinode XRT, and in hard X-rays by RHESSI. We combined these data, together with MDI longitudinal magnetograms, to get as complete a picture of the event as possible. Our emphasis is on two type-II bursts that occurred near respective maxima in the GOES light curves. The first, associated with the main peak of the event, showed an impressive fundamental-harmonic structure, while the emission of the second consisted of three well-separated bands with superposed pulsations. Using positional info...
We present observations of a UV event which occurred in a polar coronal hole. They were obtained ... more We present observations of a UV event which occurred in a polar coronal hole. They were obtained by SUMER on SOHO in several chromospheric and transition region spectral lines. Its birth site was about 50 arc sec inside the limb and in a network lane showing a net outflow before its initiation. The event had an extension of about 5 arc sec along the
One of the major discoveries of EIT on SOHO was the observation of large-scale EUV intensity dist... more One of the major discoveries of EIT on SOHO was the observation of large-scale EUV intensity disturbances which travel over significant fractions of the solar disk. These `EUV waves' are associated with CME onsets and can be either an MHD wave triggered by the eruption or the footprints of the associated CME, which currently is a subject of intense debate.
ABSTRACT Coronal mass ejection (CME) cavities seen in white-light coronagraphs expand nearly self... more ABSTRACT Coronal mass ejection (CME) cavities seen in white-light coronagraphs expand nearly self similarly in the outer corona and inner solar wind. Little is known about their initial expansion in the inner corona. A two-phase evolution, consisting of an initial overexpansion up to a heliocentric front height of about 1.5 solar radii, followed by nearly self-similar expansion, was recently discovered in STEREO/SECCHI observations of a fast CME (Patsourakos et al. 2010). The overexpansion is expressed as a decrease of the cavity aspect ratio (center height by radius) by at least a factor of 2 during the rise phase of the main CME acceleration. We present MHD simulations of erupting flux ropes that show the initial overexpansion of a cavity in line with the observed evolution. The contributions of ideal-MHD expansion and of magnetic reconnection to the growth of the flux rope and cavity in the simulations will be quantified to identify the primary cause of the overexpansion. This assesses the diagnostic potential of the overexpansion for the change of flux rope current and the role of magnetic reconnection in the early evolution of CMEs.
ABSTRACT Despite observations of thousands of coronal mass ejections (CMEs), the details of their... more ABSTRACT Despite observations of thousands of coronal mass ejections (CMEs), the details of their formation still elude us. Impulsive CMEs, in particular, originate low in the corona, and form within 10-15 mins while accelerating rapidly. This region of the corona is regularly observed by EUV imagers but the rapid CME evolution requires high cadence and relatively large fields of view. Thanks to the operation of the STEREO and SDO missions, we are currently in a unique position to address the problem of CME formation. The two missions provide almost simultaneous observations from three viewpoints with 3 EUV imagers. The EUV instruments observe in the same (or similar) channels and have highly complimentary cadences and fields of view. In this paper, we discuss a coherent picture of the birth of CMEs based on a study of the first few-minute evolution of several impulsive CMEs. These CMEs seem to first undergo an non-linear expansion followed by a self-similar phase. We discuss the implication for CME initiation models.
ABSTRACT Understanding the first moments in the life-time of Coronal Mass Ejections (CMEs), i.e. ... more ABSTRACT Understanding the first moments in the life-time of Coronal Mass Ejections (CMEs), i.e. their genesis, represents possibly the key to unlock the physical processes responsible for their initiation. After this critical interval, which could last as little as few minutes for the most impulsive events, differences between various CME models become minimal. The recent launch of the SDO mission and the availability of high-quality EUV imaging from AIA in particular, opened a new avenue into CME initiation investigations with its unprecedented image cadence and multi-wavelength simultaneous coverage. We here report on AIA observations of an impulsive CME-flare-EUV wave event which took place during 13 June 2010. All the important dynamics (e.g., rise phase of the flare, impulsive acceleration of the CME) had a duration of only 10 minutes making this event a perfect showcase event for AIA. Taking advantage of the unique aspects of AIA data (12 sec cadence and 7 different EUV channels) we present a detailed analysis of this event which includes: (1) its kinematic behavior (acceleration profile); (2) radial and expansion speeds; (3) relationships between (1) and (2) with the flare energy release; (4) multi-temperature evolution of the early CME. All the above supply new strong constraints for the physics of impulsive CMEs.
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