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Titolo:
Properties of coronal mass ejections: SOHO LASCO observations from January1996 to June 1998
Autore:
St Cyr, OC; Howard, RA; Sheeley, NR; Plunkett, SP; Michels, DJ; Paswaters, SE; Koomen, MJ; Simnett, GM; Thompson, BJ; Gurman, JB; Schwenn, R; Webb, DF; Hildner, E; Lamy, PL;
Indirizzi:
Computat Phys Inc, Fairfax, VA USA Computat Phys Inc Fairfax VA USAComputat Phys Inc, Fairfax, VA USA USN, Res Lab, Washington, DC 20375 USA USN Washington DC USA 20375USN, Res Lab, Washington, DC 20375 USA Univ Space Res Assoc, Washington, DC USA Univ Space Res Assoc Washington DC USA ace Res Assoc, Washington, DC USA Ball Aerosp Corp, Boulder, CO 80301 USA Ball Aerosp Corp Boulder CO USA 80301 Aerosp Corp, Boulder, CO 80301 USA Sachs Freeman Associates Inc, Naval Res Lab, Washington, DC 20375 USA Sachs Freeman Associates Inc Washington DC USA 20375 ington, DC 20375 USA Univ Birmingham, Sch Phys & Space Res, Birmingham B15 2TT, W Midlands, England Univ Birmingham Birmingham W Midlands England B15 2TT W Midlands, England NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA NASA Greenbelt MD USA 20771 Univ Space Res Assoc, Greenbelt, MD 20771 USA Max Planck Inst Aeron, D-37189 Lindau, Germany Max Planck Inst Aeron Lindau Germany D-37189 on, D-37189 Lindau, Germany Boston Coll, Inst Sci Res, Chestnut Hill, MA 02167 USA Boston Coll Chestnut Hill MA USA 02167 i Res, Chestnut Hill, MA 02167 USA Space Vehicles Directorate, Air Force Res Lab, Hanscom AFB, MA USA Space Vehicles Directorate Hanscom AFB MA USA s Lab, Hanscom AFB, MA USA NOAA, Space Environm Ctr, Boulder, CO 80303 USA NOAA Boulder CO USA 80303NOAA, Space Environm Ctr, Boulder, CO 80303 USA Astron Spatiale Lab, F-13248 Marseille, France Astron Spatiale Lab Marseille France F-13248 , F-13248 Marseille, France
Titolo Testata:
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
fascicolo: A8, volume: 105, anno: 2000,
pagine: 18169 - 18185
SICI:
0148-0227(20000801)105:A8<18169:POCMES>2.0.ZU;2-D
Fonte:
ISI
Lingua:
ENG
Soggetto:
DISCONNECTED MAGNETIC-STRUCTURE; SOLAR-WIND; SMM OBSERVATIONS; WHITE-LIGHT; FLOW SPEEDS; FLUX ROPE; APRIL 7; EIT; TRANSIENT; EARTH;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
73
Recensione:
Indirizzi per estratti:
Indirizzo: St Cyr, OC Computat Phys Inc, Fairfax, VA USA Computat Phys Inc Fairfax VA USA at Phys Inc, Fairfax, VA USA
Citazione:
O.C. St Cyr et al., "Properties of coronal mass ejections: SOHO LASCO observations from January1996 to June 1998", J GEO R-S P, 105(A8), 2000, pp. 18169-18185

Abstract

We report the properties of all the 841 coronal mass ejections (CMEs) observed by the Solar and Heliospheric Observatory (SOHO) Large Angle Spectroscopic Coronagraph (LASCO) C2 and C3 white-light coronagraphs from January 1996 through June 1998, and we compare those properties to previous observations by other similar instruments. Both the CME rate and the distribution ofapparent locations of CMEs varied during this period as expected based on previous solar cycles. The distribution of apparent speeds and the fractionof CMEs showing acceleration were also in agreement with earlier reports. The pointing stability provided by an L-l orbit and the use of CCD detectors have resulted in superior brightness sensitivity for LASCO over earlier coronagraphs; however, we have not detected a significant population of fainter (i.e., low mass) CMEs. The general shape of the distribution of apparent sizes for LASCO CMEs is similar to those of earlier reports, but the average (median) apparent size of 72 degrees (50 degrees) is significantly larger. The larger average apparent size is predominantly the result of the detection of a population of partial and complete halo CMEs at least some of which appear to be events with a significant longitudinal component directedalong the Sun-Earth line, either toward or away from the Earth. Using fulldisk solar images obtained by the Extreme ultraviolet Imaging Telescope (EIT) on SOHO, we found that 40 out of 92 of these events might have been directed toward the Earth, and we compared the timing of those with the I(I) geomagnetic storm index in the days following the CME, Although the "false alarm" rate was high, we found that 15 out of 21 (71%) of the K-p greater than or equal to 6 storms could be accounted for as SOHO LASCO/EIT frontside halo CMEs. If we eliminate three Kp, storms that occurred following LASCO/EIT data gaps. then the possible association rate was 15 out of 18 (83%).

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Documento generato il 26/10/20 alle ore 23:21:33