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G. Michalek

Bio: G. Michalek is an academic researcher from Jagiellonian University. The author has contributed to research in topics: Coronal mass ejection & Magnetic cloud. The author has an hindex of 20, co-authored 28 publications receiving 3171 citations. Previous affiliations of G. Michalek include The Catholic University of America & Goddard Space Flight Center.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the authors present a summary of the statistical properties of the CMEs, including the apparent central position angle, the angular width in the sky plane, and the height (heliocentric distance) as a function of time.
Abstract: [1] The Solar and Heliospheric Observatory (SOHO) mission's white light coronagraphs have observed nearly 7000 coronal mass ejections (CMEs) between 1996 and 2002. We have documented the measured properties of all these CMEs in an online catalog. We describe this catalog and present a summary of the statistical properties of the CMEs. The primary measurements made on each CME are the apparent central position angle, the angular width in the sky plane, and the height (heliocentric distance) as a function of time. The height-time measurements are then fitted to first- and second-order polynomials to derive the average apparent speed and acceleration of the CMEs. The statistical properties of CMEs are (1) the average width of normal CMEs (20° 900 km s−1) show deceleration. Solar cycle variation and statistical properties of CMEs are revealed with greater clarity in this study as compared with previous studies. Implications of our findings for CME models are discussed.

1,086 citations

Journal ArticleDOI
TL;DR: The SOHO/LASCO CME catalog as mentioned in this paper is a data base for the analysis of coronal mass ejections (CMEs) in the solar corona.
Abstract: Coronal mass ejections (CMEs) are routinely identified in the images of the solar corona obtained by the Solar and Heliospheric Observatory (SOHO) mission’s Large Angle and Spectrometric Coronagraph (LASCO) since 1996. The identified CMEs are measured and their basic attributes are cataloged in a data base known as the SOHO/LASCO CME Catalog. The Catalog also contains digital data, movies, and plots for each CME, so detailed scientific investigations can be performed on CMEs and the related phenomena such as flares, radio bursts, solar energetic particle events, and geomagnetic storms. This paper provides a brief description of the Catalog and summarizes the statistical properties of CMEs obtained using the Catalog. Data products relevant to space weather research and some CME issues that can be addressed using the Catalog are discussed. The URL of the Catalog is: http://cdaw.gsfc.nasa.gov/CME_list.

587 citations

Journal ArticleDOI
TL;DR: In this article, the association between solar energetic particle (SEP) events and coronal mass ejections (CMEs) was studied and it was shown that CME interaction is an important aspect of SEP production.
Abstract: We studied the association between solar energetic particle (SEP) events and coronal mass ejections (CMEs) and found that CME interaction is an important aspect of SEP production. Each SEP event was associated with a primary CME that is faster and wider than average CMEs and originated from west of E45°. For most of the SEP events, the primary CME overtakes one or more slower CMEs within a heliocentric distance of ∼20 R⊙. In an inverse study, we found that for all the fast (speed greater than 900 km s^(-1)) and wide (width greater than 60°) western hemispheric frontside CMEs during the study period, the SEP-associated CMEs were ∼4 times more likely to be preceded by CME interaction than the SEP-poor CMEs; i.e., CME interaction is a good discriminator between SEP-poor and SEP-associated CMEs. We infer that the efficiency of the CME-driven shocks is enhanced as they propagate through the preceding CMEs and that they accelerate SEPs from the material of the preceding CMEs rather than from the quiet solar wind. We also found a high degree of association between major SEP events and interplanetary type II radio bursts, suggesting that proton accelerators are also good electron accelerators.

242 citations

Journal ArticleDOI
TL;DR: In this article, the authors compare the statistical properties of these CMEs with those of the general population of CME observed during cycle 23 and find that the 2003 October-November CME were fast and wide on the average and hence were very energetic, nearly 20 percent of the ultrafast CME events of cycle 23 occurred during the October−November interval, including the fastest CME of the study period (∼2700 km s−1 on 4 November 2003 at 1954 UT).
Abstract: [1] Fast coronal mass ejections (CMEs), X-class flares, solar energetic particle (SEP) events, and interplanetary shocks were abundantly observed during the episode of intense solar activity in late October and early November 2003. Most of the 80 CMEs originated from three active regions (NOAA ARs 484, 486, and 488). We compare the statistical properties of these CMEs with those of the general population of CMEs observed during cycle 23. We find that (1) the 2003 October–November CMEs were fast and wide on the average and hence were very energetic, (2) nearly 20 percent of the ultrafast CMEs (speed ≥2000 km s−1) of cycle 23 occurred during the October–November interval, including the fastest CME of the study period (∼2700 km s−1 on 4 November 2003 at 1954 UT), (3) the rate of full-halo CMEs was nearly four times the average rate during cycle 23, (4) at least sixteen shocks were observed near the Sun, while eight of them were intercepted by spacecraft along the Sun-Earth line, (5) the CMEs were highly geoeffective: the resulting geomagnetic storms were among the most intense of cycle 23, (6) the CMEs were associated with very large SEP events, including the largest event of cycle 23. These extreme properties were commensurate with the size and energy of the associated active regions. This study suggests that the speed of CMEs may not be much higher than ∼3000 km s−1, consistent with the free energy available in active regions. An important practical implication of such a speed limit is that the Sun-Earth travel times of CME-driven shocks may not be less than ∼0.5 day. Two of the shocks arrived at Earth in <24 hours, the first events in ∼30 years and only the 14th and 15th documented cases of such events since 1859.

192 citations

Journal ArticleDOI
TL;DR: In this article, the visibility of coronal mass ejections (CMEs) of the Large Angle Spectrometric Coronagraph (LASCO) on board the Solar and Heliospheric Observatory (SOHO) was examined using the longitudinal variation of CME association of X-ray flares.
Abstract: [1] We report the visibility (detection efficiency) of coronal mass ejections (CMEs) of the Large Angle Spectrometric Coronagraph (LASCO) on board the Solar and Heliospheric Observatory (SOHO). We collected 1301 X-ray flare events (above C3 level) detected by the GOES satellite and examined their CME associations using data from LASCO coronagraphs. The CME visibility was examined using the longitudinal variation of CME association of X-ray flares, under the assumption that all CMEs associated with limb flares are detectable by LASCO. Our findings are (1) the CME association rate clearly increased with X-ray flare size from 20% for C-class flares (between C3 and C9 levels) to 100% for huge flares (above X3 level), (2) all CMEs associated with X-class flares were detected by the LASCO coronagraphs, while half (25–67%) of CMEs associated with C-class flares were invisible. We examined the statistical properties of the flare-associated CMEs and compared them by flare size and longitude. CMEs associated with X-class flares were significantly faster (median 1556 km/s) and wider (median 244°) than those of CMEs associated with disk C-class flares (432 km/s, 68°). We conclude that all fast and wide CMEs are detectable by LASCO, but slow and narrow CMEs may not be visible when the CMEs originate from the disk center.

171 citations


Cited by
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Journal ArticleDOI
TL;DR: In this paper, the authors present a summary of the statistical properties of the CMEs, including the apparent central position angle, the angular width in the sky plane, and the height (heliocentric distance) as a function of time.
Abstract: [1] The Solar and Heliospheric Observatory (SOHO) mission's white light coronagraphs have observed nearly 7000 coronal mass ejections (CMEs) between 1996 and 2002. We have documented the measured properties of all these CMEs in an online catalog. We describe this catalog and present a summary of the statistical properties of the CMEs. The primary measurements made on each CME are the apparent central position angle, the angular width in the sky plane, and the height (heliocentric distance) as a function of time. The height-time measurements are then fitted to first- and second-order polynomials to derive the average apparent speed and acceleration of the CMEs. The statistical properties of CMEs are (1) the average width of normal CMEs (20° 900 km s−1) show deceleration. Solar cycle variation and statistical properties of CMEs are revealed with greater clarity in this study as compared with previous studies. Implications of our findings for CME models are discussed.

1,086 citations

Journal ArticleDOI
TL;DR: Cane et al. as discussed by the authors presented a revised and updated catalog of the ≈300 near-Earth ICMEs in 1996-2009, encompassing the complete cycle 23, and summarized their basic properties and geomagnetic effects.
Abstract: In a previous study (Cane and Richardson, J. Geophys. Res. 108(A4), SSH6-1, 2003), we investigated the occurrence of interplanetary coronal mass ejections in the near-Earth solar wind during 1996 – 2002, corresponding to the increasing and maximum phases of solar cycle 23, and provided a “comprehensive” catalog of these events. In this paper, we present a revised and updated catalog of the ≈300 near-Earth ICMEs in 1996 – 2009, encompassing the complete cycle 23, and summarize their basic properties and geomagnetic effects. In particular, solar wind composition and charge state observations are now considered when identifying the ICMEs. In general, these additional data confirm the earlier identifications based predominantly on other solar wind plasma and magnetic field parameters. However, the boundaries of ICME-like plasma based on charge state/composition data may deviate significantly from those based on conventional plasma/magnetic field parameters. Furthermore, the much studied “magnetic clouds”, with flux-rope-like magnetic field configurations, may form just a substructure of the total ICME interval.

770 citations

Journal ArticleDOI
Peng-Fei Chen1
TL;DR: In this paper, a review on each stage of the CME phenomenon is presented, including their pre-eruption structure, their triggering mechanisms and the precursors indicating the initiation process, their acceleration and propagation.
Abstract: Coronal mass ejections (CMEs) are the largest-scale eruptive phenomenon in the solar system, expanding from active region-sized nonpotential magnetic structure to a much larger size. The bulk of plasma with a mass of ∼ 1011,1013 kg is hauled up all the way out to the interplanetary space with a typical velocity of several hundred or even more than 1000 km s−1, with a chance to impact our Earth, resulting in hazardous space weather conditions. They involve many other much smaller-sized solar eruptive phenomena, such as X-ray sigmoids, filament/prominence eruptions, solar flares, plasma heating and radiation, particle acceleration, EIT waves, EUV dimmings, Moreton waves, solar radio bursts, and so on. It is believed that, by shedding the accumulating magnetic energy and helicity, they complete the last link in the chain of the cycling of the solar magnetic field. In this review, I try to explicate our understanding on each stage of the fantastic phenomenon, including their pre-eruption structure, their triggering mechanisms and the precursors indicating the initiation process, their acceleration and propagation. Particular attention is paid to clarify some hot debates, e.g., whether magnetic reconnection is necessary for the eruption, whether there are two types of CMEs, how the CME frontal loop is formed, and whether halo CMEs are special.

679 citations

Journal ArticleDOI
TL;DR: The current understanding of solar flares, mainly focused on magnetohydrodynamic (MHD) processes responsible for producing a flare, can be found in this article, where the authors present a review of the models proposed to explain the physical mechanism of flares, giving an comprehensive explanation of the key processes.
Abstract: This paper outlines the current understanding of solar flares, mainly focused on magnetohydrodynamic (MHD) processes responsible for producing a flare. Observations show that flares are one of the most explosive phenomena in the atmosphere of the Sun, releasing a huge amount of energy up to about 1032 erg on the timescale of hours. Flares involve the heating of plasma, mass ejection, and particle acceleration that generates high-energy particles. The key physical processes for producing a flare are: the emergence of magnetic field from the solar interior to the solar atmosphere (flux emergence), local enhancement of electric current in the corona (formation of a current sheet), and rapid dissipation of electric current (magnetic reconnection) that causes shock heating, mass ejection, and particle acceleration. The evolution toward the onset of a flare is rather quasi-static when free energy is accumulated in the form of coronal electric current (field-aligned current, more precisely), while the dissipation of coronal current proceeds rapidly, producing various dynamic events that affect lower atmospheres such as the chromosphere and photosphere. Flares manifest such rapid dissipation of coronal current, and their theoretical modeling has been developed in accordance with observations, in which numerical simulations proved to be a strong tool reproducing the time-dependent, nonlinear evolution of a flare. We review the models proposed to explain the physical mechanism of flares, giving an comprehensive explanation of the key processes mentioned above. We start with basic properties of flares, then go into the details of energy build-up, release and transport in flares where magnetic reconnection works as the central engine to produce a flare.

677 citations

Journal ArticleDOI
TL;DR: The SOHO/LASCO CME catalog as mentioned in this paper is a data base for the analysis of coronal mass ejections (CMEs) in the solar corona.
Abstract: Coronal mass ejections (CMEs) are routinely identified in the images of the solar corona obtained by the Solar and Heliospheric Observatory (SOHO) mission’s Large Angle and Spectrometric Coronagraph (LASCO) since 1996. The identified CMEs are measured and their basic attributes are cataloged in a data base known as the SOHO/LASCO CME Catalog. The Catalog also contains digital data, movies, and plots for each CME, so detailed scientific investigations can be performed on CMEs and the related phenomena such as flares, radio bursts, solar energetic particle events, and geomagnetic storms. This paper provides a brief description of the Catalog and summarizes the statistical properties of CMEs obtained using the Catalog. Data products relevant to space weather research and some CME issues that can be addressed using the Catalog are discussed. The URL of the Catalog is: http://cdaw.gsfc.nasa.gov/CME_list.

587 citations