Problems of differentiation of flares with respect to geophysical effects

Dodson, Helen W.; Hedeman, E. Ruth

doi:10.1016/0032-0633(64)90034-0

Cited by 28 publications

(18 citation statements)

References 33 publications

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“…Such an investigation is also of interest for the study of solar magnetic fields. Indeed, recent observations (Frank and Gurnett, 1972;Alvarez et al, 1972;Linet al, 1973) have clearly shown that type III bursts are excited by fast electrons, in full agreement with the plasma hypothesis initiated by Wild et al (1959). These particles are escaping through the corona and the interplanetary medium on a scatter free mode.…”

Section: Introductionsupporting

confidence: 68%

On the role of the magnetic configuration of flares for production of type III solar radio bursts

Axisa

1974

Sol Phys

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This paper investigates the possibility that the particular location of flare production sites in an active region is intimately connected to the production of type III radio bursts as well as centimetric and hard X-ray events.For the few active regions analysed (viz. McMath 8863, 8905, 8907 and 8921) it is shown that even a crude statistical test is sufficient in revealing significant differences concerning the emissions of these radiations by flares located in various flare production sites. In particular, flares located outside the general bipolar pattern of the active region are characterized by a higher type III flare association rate ( >~ 50 %) than those taking place inside of it ( ~< 20 %). Centimetric and hard X-ray events are more likely to be expected in connection with flares located inside strong magnetic fields arising from well developed sunspots. Such results are pointing out that the concept of 'flare production sites' is important not only in relation with the Ha flare activity but also in relation with the non-thermal emissions accompanying the flares.Probably this is due to changing magnetic configuration from one flare site to the other.

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Section: Introductionsupporting

confidence: 68%

On the role of the magnetic configuration of flares for production of type III solar radio bursts

Axisa

1974

Sol Phys

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“…The type of SID for which worldwide coverage has been most nearly complete in recent years is the Short-Wave Fade (SWF). We therefore have studied the occurrence of SWF's with the 69 flares of importance N2 in regions with small or no spots, 1956-1969, and have compared the results with similar information for all flares of importance ~2 observed during the IGY (1957IGY ( .5-1958 (Dodson and Hedeman, 1964). A summary of this comparison is shown in Table III.…”

Section: Ionizing Radiationmentioning

confidence: 99%

“…Approximately 80?/0 of the flares of importance )2 were accompanied by X-ray enhancement (2-12 A) at least as great as 4 times the ambient quiet Sun, whether or not they were located in regions with significant spots. For X-ray bursts of greater intensity, flares in spotted Dodson and Hedeman (1964).…”

Section: Ionizing Radiationmentioning

confidence: 99%

Major H? flares in centers of activity with very small or no spots

Dodson

Hedeman

1970

Sol Phys

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Major Ha flares (importance ~2) in plages with only small or no spots constitute a rare but well observed aspect of solar activity. Information relating to 83 such flares has been assembled and studied. In the years 1956-1968 these flares represented ~ 7~ of all confirmed flares of importance 2. In general, the flares were of unusually long duration and rose to maximum intensity slowly. A flash phase was often absent or poorly defined. In a number of cases, the flare emission included two bright filaments more or less parallel. The flares usually occurred during the late, flare-poor phase of a center of activity, and their outbreak did not presage a resurgence of activity in subsequent rotations. The flares were frequently associated with the position of dark filaments.Like major flares in general, the flares in regions with small or no spots usually were associated with long-enduring radiation (gradual rise and fall and/or postburst increase) at ~ 10 cm, and with X-ray enhancements (2-12/~) at least as great as 4 times the quiet Sun. They were deficient, in the associated occurrence of strong, impulsive, centimetfic bursts and of X-ray events > 20 times the quiet Sun. The absence of large spots apparently did not inhibit the occurrence of Type II bursts.Only 41% of the major flares here studied were accompanied by shortwave fades and of these ionospheric disturbances only a few were great events. In general the flares were not followed by the detection of high energy particles or the onset of geomagnetic storms. However, a few of the flares (including those of 1967 January 11 and February 13) apparently were associated with well observed particle emission and suggest that the presence of a large complex spot is not always necessary for the acceleration of energetic particles or the emission of solar plasma at the time of a large Hc~ flare.

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“…http://www.livingreviews.org/lrsp-2012-3 3.8 "Problem" and "stealth" CMEs So-called "problem" geomagnetic storms lack historically obvious signatures of related solar activity, such as flares and large disappearing filaments (e.g., Dodson and Hedeman, 1964;McAllister et al, 1996, and references therein). An event on 6 -10 January 1997 was the first such problem storm for which the antecedent CME was actually observed (Webb et al, 2000b).…”

Section: Living Reviews In Solar Physicsmentioning

confidence: 99%

Coronal Mass Ejections: Observations

Webb

Howard

2012

Living Rev. Solar Phys.

649

534

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Solar eruptive phenomena embrace a variety of eruptions, including flares, solar energetic particles, and radio bursts. Since the vast majority of these are associated with the eruption, development, and evolution of coronal mass ejections (CMEs), we focus on CME observations in this review. CMEs are a key aspect of coronal and interplanetary dynamics. They inject large quantities of mass and magnetic flux into the heliosphere, causing major transient disturbances. CMEs can drive interplanetary shocks, a key source of solar energetic particles and are known to be the major contributor to severe space weather at the Earth. Studies over the past decade using the data sets from (among others) the SOHO, TRACE, Wind, ACE, STEREO, and SDO spacecraft, along with ground-based instruments, have improved our knowledge of the origins and development of CMEs at the Sun and how they contribute to space weather at Earth. SOHO, launched in 1995, has provided us with almost continuous coverage of the solar corona over more than a complete solar cycle, and the heliospheric imagers SMEI (2003 -2011) and the HIs (operating since early 2007) have provided us with the capability to image and track CMEs continually across the inner heliosphere. We review some key coronal properties of CMEs, their source regions and their propagation through the solar wind. The LASCO coronagraphs routinely observe CMEs launched along the Sun-Earth line as halo-like brightenings. STEREO also permits observing Earth-directed CMEs from three different viewpoints of increasing azimuthal separation, thereby enabling the estimation of their three-dimensional properties. These are important not only for space weather prediction purposes, but also for understanding the development and internal structure of CMEs since we view their source regions on the solar disk and can measure their in-situ characteristics along their axes. Included in our discussion of the recent developments in CME-related phenomena are the latest developments from the STEREO and LASCO coronagraphs and the SMEI and HI heliospheric imagers.

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Problems of differentiation of flares with respect to geophysical effects

Cited by 28 publications

References 33 publications

On the role of the magnetic configuration of flares for production of type III solar radio bursts

On the role of the magnetic configuration of flares for production of type III solar radio bursts

Major H? flares in centers of activity with very small or no spots

Coronal Mass Ejections: Observations

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