Detailed comparison of downflows seen both  in EIT 30.4 nm and Big Bear H<i>α</i> movies

Groof, A. De; Bastiaensen, C.; Müller, D.; Berghmans, D.; Poedts, Stefaan

doi:10.1051/0004-6361:20053129

Cited by 57 publications

(45 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Coronal rain are cool dense blobs that form in warm active region loops and fall along the guiding magnetic field to the solar surface (Kawaguchi 1970;Leroy 1972;Athay et al 1980;Schrijver 2001;De Groof et al 2004;de Groof et al 2005;Vashalomidze et al 2015). They are traditionally observed in chromospheric lines, such as H-α or Ca II H, as well as in transition region lines.…”

Section: Introductionmentioning

confidence: 99%

Kinematics of coronal rain in a transversely oscillating loop: Ponderomotive force and rain-excited oscillations

Verwichte

Antolin

Rowlands

et al. 2017

A&A

View full text Add to dashboard Cite

Context. Coronal rain is composed of cool dense blobs that form in solar coronal loops and are a manifestation of catastrophic cooling linked to thermal instability. Once formed, rain falls towards the solar surface at sub-ballistic speeds, which is not well understood. Pressure forces seem to be the prime candidate to explain this. In many observations rain is accompanied by transverse oscillations and the interaction between rain and these oscillations needs to be explored. Aims. Therefore, an alternative kinematic model for coronal rain kinematics in transversely oscillating loops is developed to understand the physical nature of the observed sub-ballistic falling motion of rain. This model explicitly explores the role of the ponderomotive force arising from the transverse oscillation on the rain motion and the capacity of rain to excite wave motion.Methods. An analytical model is presented that describes a rain blob guided by the coronal magnetic field supporting a onedimensional shear Alfvén wave as a point mass on an oscillating string. The model includes gravity and the ponderomotive force from the oscillation acting on the mass and the inertia of the mass acting on the oscillation. Results. The kinematics of rain in the limit of negligible rain mass are explored and falling and trapped regimes are found, depending on wave amplitude. In the trapped regime for the fundamental mode, the rain blob bounces back and forth around the loop top at a long period that is inversely proportional to the oscillation amplitude. The model is compared with several observational rain studies, including one in-depth comparison with an observation that shows rain with up-and-down bobbing motion. The role of rain inertia in exciting transverse oscillations is explored in inclined loops. Conclusions. It is found that the model requires displacement amplitudes of the transverse oscillation that are typically an order of magnitude larger than observed to explain the measured sub-ballistic motion of the rain. Therefore, it is concluded that the ponderomotive force is not the primary reason for understanding sub-ballistic motion, but it plays a role in cases of large loop oscillations. The appearance of rain causes the excitation of small-amplitude transverse oscillations that may explain observed events and provide a seismological tool to measure rain mass.

show abstract

Section: Introductionmentioning

confidence: 99%

Kinematics of coronal rain in a transversely oscillating loop: Ponderomotive force and rain-excited oscillations

Verwichte

Antolin

Rowlands

et al. 2017

A&A

View full text Add to dashboard Cite

show abstract

“…Müller et al 2005;Klimchuk et al 2008). They are observed in chromospheric and transition region lines as dense blobs of plasma that form near the top of loops and then fall towards the solar surface guided by the magnetic field (Schrijver 2001;De Groof et al 2004;de Groof et al 2005). Recent observations from the Solar Optical Telescope (SOT) on board Hinode, the Interface Region Imaging Spectrograph (IRIS), and ground-based observatories such as the Swedish Solar Telescope have demonstrated coronal rain is a common occurrence (e.g.…”

Section: Introductionmentioning

confidence: 99%

Excitation and evolution of vertically polarised transverse loop oscillations by coronal rain

Verwichte

Kohutova

2017

A&A

View full text Add to dashboard Cite

Context. Coronal rain is composed of cool dense blobs that form in solar coronal loops and are a manifestation of catastrophic cooling linked to thermal instability. The nature and excitation of oscillations associated with coronal rain is not well understood. Aims. We consider observations of coronal rain in a bid to elucidate the excitation mechanism and evolution of wave characteristics. Methods. We analyse IRIS and Hinode/SOT observations of an oscillating coronal rain event on 17 Aug 2014 and determine the wave characteristics as a function of time using tried and tested time-space analysis techniques. Results. We exploit the seismological capability of the oscillation to deduce the relative rain mass from the oscillation amplitude. This is consistent with the evolution of the oscillation period showing the loop loosing a third of its mass due to falling coronal rain in a 10-15 minute time period. Conclusions. We present first evidence of the excitation of vertically polarised transverse loop oscillations triggered by a catastrophic cooling at the loop top and consistent with two thirds of the loop mass comprising of cool rain mass.

show abstract

“…Based on EIT 304 Å observations de Groof et al (2004) Movies are available in electronic form at http://www.aanda.org presented bright coronal downflows in a coronal loop without any associated eruption. The origin of these downflows was explained by numerical simulations of "catastrophic cooling" in a coronal loop which is heated predominantly at its footpoints (de Groof et al 2005).…”

Section: Introductionmentioning

confidence: 99%

A bright coronal downflow seen in multi-wavelength observations: evidence of a bifurcating flux-rope?

Tripathi

Solanki²,

Mason

et al. 2007

A&A

View full text Add to dashboard Cite

Aims. We study the origin and characteristics of a bright coronal downflow seen after a coronal mass ejection associated with erupting prominences on 5 March 2000. Methods. This study extends that of Tripathi et al. (2006b, A&A, 449, 369) based on the Extreme-ultraviolet Imaging Telescope (EIT), the Soft X-ray Telescope (SXT) and the Large Angle Spectrometric Coronagraph (LASCO) observations. We combined those results with an analysis of the observations taken by the Hα and the Mk4 coronagraphs at the Mauna Loa Solar Observatory (MLSO). The combined data-set spans a broad range of temperature as well as continuous observations from the solar surface out to 30 R . Results. The downflow started at around 1.6 R and contained both hot and cold gas. The downflow was observed in the Hα and the Mk4 coronagraphs as well as the EIT and the SXT and was approximately co-spatial and co-temporal providing evidence of multi-thermal plasma. The Hα and Mk4 images show cusp-shaped structures close to the location where the downflow started. Mk4 observations reveal that the speed of the downflow in the early phase was substantially higher than the free-fall speed, implying a strong downward acceleration near the height at which the downflow started. Conclusions. The origin of the downflow was likely to have been magnetic reconnection taking place inside the erupting flux rope that led to its bifurcation.

show abstract

Detailed comparison of downflows seen both in EIT 30.4 nm and Big Bear Hα movies

Cited by 57 publications

References 22 publications

Kinematics of coronal rain in a transversely oscillating loop: Ponderomotive force and rain-excited oscillations

Kinematics of coronal rain in a transversely oscillating loop: Ponderomotive force and rain-excited oscillations

Excitation and evolution of vertically polarised transverse loop oscillations by coronal rain

A bright coronal downflow seen in multi-wavelength observations: evidence of a bifurcating flux-rope?

Contact Info

Product

Resources

About