Identification

Title

STEREO quadrature observations of coronal dimming at the onset of mini-CMEs

Abstract

Context. Using unique quadrature observations with the two STEREO spacecraft, we investigate coronal dimmings at the onset of small-scale eruptions. In CMEs they are believed to indicate the opening up of the coronal magnetic fields at the start of the eruption. Aims: It is to determine whether coronal dimming seen in small-scale eruptions starts before or after chromospheric plasma ejection. Methods: One STEREO spacecraft obtained high cadence, 75 s, images in the He II 304 Å channel, and the other simultaneous images in the Fe IX/Fe X 171 Å channel. We concentrate on two well-positioned chromospheric eruptions that occurred at disk center in the 171 Å images, and on the limb in 304 Å. One was in the quiet Sun and the other was in an equatorial coronal hole. We compare the timing of chromospheric eruption seen in the 304 Å limb images with the brightenings and dimmings seen on disk in the 171 Å images. Further we use off-limb images of the low frequency 171 Å power to infer the coronal structure near the eruptions. Results: In both the quiet Sun and the coronal hole eruption, on disk 171 Å dimming was seen before the chromospheric eruption, and in both cases it extends beyond the site of the chromospheric eruption. The quiet Sun eruption occurred on the outer edge of the enclosing magnetic field of a prominence and may be related to a small disruption of the prominence just before the 171 Å dimming. Conclusions: These small-scale chromospheric eruptions started with a dimming in coronal emission just like their larger counterparts. We therefore suggest that a fundamental step in triggering them was the removal of overlying coronal field.

Resource type

document

Resource locator

Unique resource identifier

code

http://n2t.net/ark:/85065/d7v69k1v

codeSpace

Dataset language

eng

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geoscientificInformation

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Text

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title

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reference date

date type

publication

effective date

2016-01-01T00:00:00Z

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publication

effective date

2010-07-01T00:00:00Z

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None

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Responsible party

contact position

OpenSky Support

organisation name

UCAR/NCAR - Library

full postal address

PO Box 3000

Boulder

80307-3000

email address

opensky@ucar.edu

web address

http://opensky.ucar.edu/

name: homepage

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pointOfContact

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