Magnetic reconnection processes induced by a CME expansion

Abstract. On 10–11 December 2005 a slow CME occurred in the Western Hemisphere in between two coronal streamers. SOHO/MDI magnetograms show a multipolar magnetic configuration at the photosphere: a complex of active regions located at the CME source and two bipoles at the base of the lateral coronal streamers. White light observations reveal that the CME expansion affects both of them and induces the release of plasma within or close to the nearby streamers. These transient phenomena are possibly due to magnetic reconnections induced by the CME expansion and occurring inside the streamer current sheet or between the CME flanks and the streamer. These events have been observed by the SOHO/UVCS with the spectrometer slit centered at 1.8 R⊙ over about a full day. In this work we focus on the interaction between the CME and the streamer: the UVCS spectral interval included UV lines from ions at different temperatures of maximum formation such as O VI, Si XIII and Al Xi. These data gave us the opportunity to infer the evolution of plasma temperature and density at the reconnection site and adjacent regions. These are relevant to characterize secondary reconnection processes occurring during a CME development.

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The role of lateral magnetic reconnection in solar eruptive events

Annales Geophysicae ◽

10.5194/angeo-27-3941-2009 ◽

2009 ◽

Vol 27 (10) ◽

pp. 3941-3948 ◽

Cited By ~ 1

Author(s):

A. Soenen ◽

A. Bemporad ◽

C. Jacobs ◽

S. Poedts

Keyword(s):

Numerical Simulations ◽

White Light ◽

Flux Rope ◽

Active Regions ◽

Western Hemisphere ◽

Transient Phenomena ◽

Single Location ◽

Magnetic Tension ◽

Coronal Streamers

Abstract. On 10–11 December 2005 a slow CME occurred in between two coronal streamers in the Western Hemisphere. SOHO/MDI magnetograms show a multipolar magnetic configuration at the photosphere consisting of a complex of active regions located at the CME source and two bipoles at the base of the lateral coronal streamers. White light observations reveal that the expanding CME affects both of the lateral streamers and induces the release of plasma within or close to them. These transient phenomena are possibly due to magnetic reconnections induced by the CME expansion that occurs either inside the streamer current sheet or between the CME flanks and the streamer. Our observations show that CMEs can be associated to not only a single reconnection process at a single location in the corona, but also to many reconnection processes occurring at different times and locations around the flux rope. Numerical simulations are used to demonstrate that the observed lateral reconnections can be reproduced. The observed secondary reconnections associated to CMEs may facilitate the CME release by globally decreasing the magnetic tension of the corona. Future CME models should therefore take into account the lateral reconnection effect.

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Consistency of teleseismic reporting since 1963

Bulletin of the Seismological Society of America ◽

10.1785/bssa0720010093 ◽

1982 ◽

Vol 72 (1) ◽

pp. 93-111

Author(s):

R. E. Habermann

Keyword(s):

Detection System ◽

Active Regions ◽

The United States ◽

Western Hemisphere ◽

Cumulative Number ◽

Data Set ◽

Seismicity Rate ◽

Teleseismic Data ◽

Entire World ◽

Seismicity Rate Changes

abstract Changes in the rate of occurrence of smaller events have been recognized in the rupture zones of upcoming large earthquakes in several postearthquake and one preearthquake study. A data set in which a constant portion of the events in any magnitude band are consistently reported through time is crucial for the recognition of seismicity rate changes which are real (related to some process change in the earth). Such a data set is termed a homogeneous data set. The consistency of reporting of earthquakes in the NOAA Hypocenter Data File (HDF) since 1963 is evaluated by examining the cumulative number of events reported as a function of time for the entire world in eight magnitude bands. It is assumed that the rate of occurrence of events in the entire world is roughly constant on the time scale examined here because of the great size of the worldwide earthquake production system. The rate of reporting of events with magnitudes above mb = 4.5 has been constant or increasing since 1963. Significant decreases in the number of events reported per month in the magnitude bands below mb = 4.4 occurred during 1968 and 1976. These decreases are interpreted as indications of decreases in detection of events for two reasons. First, they occur at times of constant rates of occurrence and reporting of larger events. Second, the decrease during the late 1960's has also been recognized in the teleseismic data reported by the International Seismological Centre (ISC). This suggests that the decrease in the number of small events reported was related to facets of the earthquake reporting system which the ISC and NOAA share. The most obvious candidate is the detection system. During 1968, detection decreased in the United States, Central and South America, and portions of the South Pacific. This decrease is probably due to the closure of the VELA arrays, BMO, TFO, CPO, UBO, and WMO. During 1976, detection decreased in most of the seismically active regions of the western hemisphere, as well as in the region between Kamchatka and Guam. The cause of this detection decrease is unclear. These detection decreases seriously affect the amount of homogeneous background period available for the study of teleseismic seismicity rate changes. If events below the minimum magnitude of homogeneity are eliminated from the teleseismic data sets the resulting small numbers of events render many regions unsuitable for study. Many authors have reported seismicity rate decreases as possible precursors to great earthquakes. Few of these authors have considered detection decreases as possible explanations for their results. This analysis indicates that such considerations cannot be avoided in studies of teleseismic data.

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Expulsion of Magnetized Plasmas from Coronae

Symposium - International Astronomical Union ◽

10.1017/s007418090003014x ◽

1983 ◽

Vol 102 ◽

pp. 467-471

Author(s):

B. C. Low

Keyword(s):

Solar Corona ◽

White Light ◽

Magnetized Plasmas ◽

Transient Phenomena

A theory of the white light transient phenomena in the solar corona is given, based on recent analytic treatments of magnetohydrodynamics.

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The Large-Scale Structure of the Corona

Highlights of Astronomy ◽

10.1017/s1539299600004445 ◽

1980 ◽

Vol 5 ◽

pp. 549-556

Author(s):

Jack B. Zirker

Keyword(s):

Solar Corona ◽

White Light ◽

Large Scale ◽

Dimensional Space ◽

Coronal Holes ◽

Solar Limb ◽

Active Regions ◽

Large Scale Structure ◽

Scale Structure ◽

Fast Wind

The solar corona serves as a prototype of the outer atmospheres of all cool stars. Because of its nearness we can study this prototype in more detail than any other example. Considerable progress has been made recently in understanding how the large scale structure of the solar corona controls the genesis of the solar wind and the distribution of slow and fast wind streams throughout the three-dimensional space surrounding the sun. In this review we will discuss some of the progress made in this field during the last few years. We will emphasize the observational data and the inferences that can be made more or less directly from them. T. Holzer will discuss the theoretical aspects of stellar wind acceleration in another paper in this symposium.The large scale structures of the solar corona consist essentially of three kinds: streamers, active regions and coronal holes. Figure 1 is a familiar photograph of the solar corona, obtained in white light at the total eclipse of 30 June 1973 by the High Altitude Observatory. The streamers are the petal-like structures extending out from the black lunar limb. They taper to narrow radial spikes that have been traced out as far as 10-12 solar radii (Keller, 1979). Daily measurements of the white light corona at the Mauna Loa Observatory (Hundhausen et al. 1979) and the Pic-du-Midi Observatory (Dollfus et al., 1977) since 1965 show that the streamers are fan-shaped structures that may extend 120° in solar longitude. We see them in various perspectives at the solar limb.

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LUCI onboard Lagrange, the next generation of EUV space weather monitoring

Journal of Space Weather and Space Climate ◽

10.1051/swsc/2020052 ◽

2020 ◽

Vol 10 ◽

pp. 49

Author(s):

Matthew J. West ◽

Christian Kintziger ◽

Margit Haberreiter ◽

Manfred Gyo ◽

David Berghmans ◽

...

Keyword(s):

Space Weather ◽

Extreme Ultraviolet ◽

Coronal Holes ◽

Active Regions ◽

Pass Band ◽

The Sun ◽

Lower Corona ◽

Transient Phenomena ◽

Weather Forecasts ◽

Active Pixel

Lagrange eUv Coronal Imager (LUCI) is a solar imager in the Extreme UltraViolet (EUV) that is being developed as part of the Lagrange mission, a mission designed to be positioned at the L5 Lagrangian point to monitor space weather from its source on the Sun, through the heliosphere, to the Earth. LUCI will use an off-axis two mirror design equipped with an EUV enhanced active pixel sensor. This type of detector has advantages that promise to be very beneficial for monitoring the source of space weather in the EUV. LUCI will also have a novel off-axis wide field-of-view, designed to observe the solar disk, the lower corona, and the extended solar atmosphere close to the Sun–Earth line. LUCI will provide solar coronal images at a 2–3 min cadence in a pass-band centred on 19.5. Observations made through this pass-band allow for the detection and monitoring of semi-static coronal structures such as coronal holes, prominences, and active regions; as well as transient phenomena such as solar flares, limb coronal mass ejections (CMEs), EUV waves, and coronal dimmings. The LUCI data will complement EUV solar observations provided by instruments located along the Sun–Earth line such as PROBA2-SWAP, SUVI-GOES and SDO-AIA, as well as provide unique observations to improve space weather forecasts. Together with a suite of other remote-sensing and in-situ instruments onboard Lagrange, LUCI will provide science quality operational observations for space weather monitoring.

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Solar plasma temperature diagnostics in flares and active regions from spectral lines in the range 280–330 Å in the SPIRIT/CORONAS-F experiment

Astronomy Letters ◽

10.1134/s1063773710010056 ◽

2010 ◽

Vol 36 (1) ◽

pp. 44-58 ◽

Cited By ~ 15

Author(s):

S. V. Shestov ◽

S. V. Kuzin ◽

A. M. Urnov ◽

A. S. Ul’yanov ◽

S. A. Bogachev

Keyword(s):

Plasma Temperature ◽

Active Regions ◽

Spectral Lines ◽

Solar Plasma ◽

Temperature Diagnostics

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Location of the Sources of 19 Mc/s Solar Bursts

Australian Journal of Physics ◽

10.1071/ph590357 ◽

1959 ◽

Vol 12 (4) ◽

pp. 357 ◽

Cited By ~ 16

Author(s):

CA Shain ◽

CS Higgins

Keyword(s):

Plasma Levels ◽

Radial Distance ◽

Active Regions ◽

Reliable Data ◽

Optically Active ◽

Radio Sources ◽

The Sun ◽

Solar Bursts ◽

Coronal Streamers

By using large aerials in a new way, it has been possible to locate, with considerable accuracy, the sources of 19 Mcls solar bursts. The positions of these sources have been correlated with the positions of optically active regions associated with them, and the radial distances of the radio sources from the centre of the Sun have been deduced. In 1950-1951, 18�3 Mcls bursts came from sources at a radial distance estimated as 3�4Ro ; more reliable data in 1957 indicated that the sources of 19�7 Mcls bursts were at a radial distance of 2� 9Ro It is thought that these measurements give the distances of the fundamental plasma levels in coronal streamers.

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The White-Light and Emission Coronae at the July 22, 1990 Eclipse

International Astronomical Union Colloquium ◽

10.1017/s0252921100026026 ◽

1994 ◽

Vol 144 ◽

pp. 555-557

Author(s):

V. Rušin ◽

E. Marková

Keyword(s):

Solar Corona ◽

Coronal Hole ◽

White Light ◽

Active Regions ◽

Coronal Line ◽

Line Intensities ◽

Rapid Changes ◽

Southwest Region ◽

White Light Corona

AbstractVarious instruments were used to study the solar corona at the July 22, 1990 eclipse. The white-light corona of July 22, 1990 is of maximum type (the Ludendorff index of the corona’s shape turns out to be a+b = 0.04). There are many streamers nearly equally distributed around the whole Sun, except of the southwest region where large coronal hole was located. The green (530.3 nm) and red (637.4 nm) coronal line intensities display many rapid changes in active regions around the eclipse day. Huge prominences were located above the E-limb. The estimated total brightness of the white-light corona (WLC) reached its value ofJK= 1.32 × 10−6.

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