scholarly journals Solar Coronal Mass Ejections

1990 ◽  
Vol 140 ◽  
pp. 16-16
Author(s):  
A. J. Hundhausen ◽  
D. G. Sime ◽  
B. C. Low
Keyword(s):  
Magnetic Field ◽  
Solar Activity ◽  
Coronal Mass Ejections ◽  
Large Scale ◽  
Interplanetary Space ◽  
Field Of View ◽  
Solar Activity Minimum ◽  
Eruptive Prominence ◽  
Activity Maximum ◽  
Mass Ejection

In addition to the more or less steady solar wind, the Sun also ejects mass in highly time dependent events taking place in the corona once every few days at solar activity minimum and as often as three times a day at solar activity maximum (Hundhausen 1988, Low 1986). These events involve large scale reconfiguration of the corona with an expulsion of some 1015g of ionized material into interplanetary space. The High Altitude Observatory (HAO) operates a groundbased internally occulted coronagraph at Mauna Loa, Hawaii, with a field of view of the corona from 1.2 to 2.2R⊙ in heliocentric distance, registering polarization brightness. A second instrument at the same site in Hawaii observes the solar limb in Hα emission to detect chromospheric material from the limb out to 1.5R⊙. HAO also operates an externally occulted coronagraph/polarimeter onboard the NASA Solar Maximum Mission Satellite (SMM) launched in 1980, capitalizing on the advantage of space with a field of view from 1.5 to 6R⊙ to cover the fainter outer corona. Coronal mass ejections involve magnetic field reconfiguration from high in the corona down to the base lying below 1.1R⊙. Important physical insights can be had when simultaneous observations by HAO's three instruments are put together with a common scale and orientation to reveal a mass ejection in the full extent of the solar atmosphere from the limb outward. Combined observations of two mass ejections are presented, one associated with an eruptive prominence and the the other associated with a flare. The significance of these two events is that in both cases, the mass ejection was in fully developed motion and had traveled high into the corona well before the onset of the associated prominence or flare eruption, pointing to an instability in the large scale coronal magnetic field as the underlying cause of the global reconfiguration.

scholarly journals The Dynamics of Solar Coronal Magnetic Fields

1990 ◽  
Vol 140 ◽  
pp. 13-15
Author(s):  
B. C. Low
Keyword(s):  
Solar Activity ◽  
Large Scale ◽  
Interplanetary Space ◽  
Scattered Light ◽  
Magnetic Polarity ◽  
Half Cycle ◽  
Solar Activity Minimum ◽  
Activity Maximum ◽  
Mass Ejection

The solar corona is a hot (106K) highly ionized plasma structured by its magnetic field into open regions where the solar wind escapes and closed regions where relatively dense plasma is trapped in near static equilibrium. Observed in Thomson-scattered light at times of solar eclipse or by artificial occultation using a coronagraph, these closed regions show up conspicuously as helmet-shaped bright structures. The large scale corona evolves in time in response to the solar dynamo that continually injects new magnetic flux into the corona with the eventual reversal of the global magnetic polarity at the end of each half cycle of eleven years. It was discovered in the 1970s using spaceborne coronagraphs that in addition to its long-term evolution, the corona also undergoes dynamical reconfiguration with ejection of mass of the order of 1015g into interplanetary space (MacQueen 1980). These time dependent phenomena take place once every few days at solar activity minimum and as often three times a day at solar activity maximum. Since the 1970s, coronal mass ejections have been studied at the High Altitude Observatory by the use of the coronagraph on the NASA Solar Maximum Mission Satellite and groundbased instruments at Hawaii. This brief review presents three points of interest in the coronal mass ejection as a hydromagnetic process, emphasizing the unique opportunity offered by the corona to study hydromagnetic phenomena by direct observation (Hundhausen 1987, Kahler 1987, Low 1986).

Using Ghost Fronts to Predict the Arrival Time of CMEs during 13-17 June 2012

2020 ◽  
Author(s):  
Yutian Chi ◽  
Chris Scott ◽  
Chenglong Shen ◽  
Yuming Wang
Keyword(s):  
Coronal Mass Ejections ◽  
Large Scale ◽  
Arrival Time ◽  
Interplanetary Space ◽  
In Situ Measurements ◽  
Magnetized Plasma ◽  
Field Of View ◽  
Physical Boundary

<div> <div> <div>Coronal mass ejections (CME) are large-scale eruptions of magnetized plasma and huge energy through the corona and out into interplanetary space. <div>A mount of CMEs observed by HI-1 cameras present two fronts that are similar in shape but separated by a few degrees in elongation. Scott et al. (2019) interpret the ghost fronts as projections of separate discrete sections of the physical boundary of the  CME. Ghost fronts could provide information about the longitudinal shape of CME in the field of view of Hi- 1, which can be used to improve the forecast of the arrival time of ICME. During 13-15 June 2012, STEREO/SECCHI recorded two successive launched Earth-directed CMEs. Both of the two CMEs show clearly two fronts in HI-1 images. We use the ghost fronts to predict the arrival time of the two CMEs and utility the in-situ measurements from VEX and Wind to verify the accuracy of the prediction of ghost fronts model. </div> </div> </div> </div>

THE SOURCE REGIONS OF CORONAL MASS EJECTIONS

2013 ◽  
Vol 23 ◽  
pp. 459-466
Author(s):  
GUIPING ZHOU
Keyword(s):  
Magnetic Flux ◽  
Coronal Mass Ejection ◽  
Coronal Mass Ejections ◽  
Large Scale ◽  
Interplanetary Space ◽  
Activity Analysis ◽  
Angular Width ◽  
Source Regions ◽  
Paper Review ◽  
Mass Ejection

Coronal Mass Ejection is an entire process leading to the ejection of mass and magnetic flux into interplanetary space. Its source is studied by analyzing the associated surface activity. Analysis results show that CMEs have large-scale magnetic source structures, which provide their energy, initiation, and final angular width. This paper review the studies of CME source regions with laying emphasis on their large-scale source structures.

scholarly journals The Observed Relationships Between Some Solar Rotation Parameters and the Activity Cycle

1983 ◽  
Vol 102 ◽  
pp. 99-111
Author(s):  
Robert Howard ◽  
Barry J. LaBonte
Keyword(s):  
Solar Activity ◽  
Solar Rotation ◽  
Rotational Velocity ◽  
Torsional Oscillation ◽  
Periodic Oscillation ◽  
Activity Cycle ◽  
Solar Activity Cycle ◽  
Solar Activity Minimum ◽  
Activity Maximum ◽  
Open Question

Several parameters of the solar rotation show variations which appear to relate to the phase of the solar activity cycle. The latitude gradient of the differential rotation, as seen in the coefficients of the sin2 and sin4 terms in the latitude expansion, shows marked variations with the cycle. One of these variations may be described as a one-cycle-per-hemisphere torsional oscillation with a period of 11 years, where the high latitudes rotate faster at solar activity maximum and slower at minimum, and the low latitudes rotate faster at solar activity minimum and slower at maximum. Another variation is a periodic oscillation of the fractional difference in the low-latitude rotation between north and south hemispheres. The possibility of a variation in the absolute rotational velocity of the sun in phase with the solar cycle remains an open question. The two-cycle-per-hemisphere torsional waves in the solar rotation also represent an aspect of the rotation which varies with the cycle. We show that the amplitude of the fast flowing zone rises a year before the rise to activity maximum. The fast zone seems to be physically the more significant of the two zones.

About the Relation Between the Limb Effect of the Redshift on the Sun and the Large-Scale Distribution of Solar activity

1976 ◽  
Vol 71 ◽  
pp. 113-118
Author(s):  
P. Ambrož
Keyword(s):  
Magnetic Field ◽  
Solar Activity ◽  
Magnetic Fields ◽  
Interplanetary Magnetic Field ◽  
Large Scale ◽  
The Sun ◽  
Limb Effect

The measurement of the magnitude of the limb effect was homogenized in time and a recurrent period of maxima of 27.8 days was found. A relation was found between the maximum values of the limb effect of the redshift, the boundaries of polarities of the interplanetary magnetic field, the characteristic large-scale distribution of the background magnetic fields and the complex of solar activity.

scholarly journals On the Association between Coronal Mass Ejections and Coronal Holes

1989 ◽  
Vol 104 (2) ◽  
pp. 239-242
Author(s):  
V.K. Verma ◽  
M.C. Pande
Keyword(s):  
Magnetic Field ◽  
Coronal Mass Ejection ◽  
Coronal Mass Ejections ◽  
Solar Flares ◽  
Coronal Holes ◽  
Mass Ejection ◽  
Open Magnetic Field

AbstractThe coronal mass ejection (CME) data and the data for coronal holes for the period 1979-1982 are compared locationwise. Out of 79 CMEs whose locations and spans are known, 48 (61%) CMEs are associated with coronal holes. We make a tentative suggestion that probably the mass ejected during solar flares and active prominences may move along the open magnetic field of the coronal holes and appear as CMEs.

scholarly journals The Motion of Charged Dust Particles in Interplanetary Space

1980 ◽  
Vol 90 ◽  
pp. 309-310
Author(s):  
G. E. Morfill ◽  
E. Grün
Keyword(s):  
Magnetic Field ◽  
Current Sheet ◽  
Equatorial Plane ◽  
Particle Motion ◽  
Large Scale ◽  
Interplanetary Space ◽  
Dust Particles ◽  
Charged Dust ◽  
Particle Orbits ◽  
Interplanetary Plasma

The problem of electromagnetic perturbations of charged dust particle orbits in interplanetary space has been re-examined in the light of our better understanding of the large scale spatial and temporal interplanetary plasma and field topology. In the equatorial plane, the magnetic sectors, caused by the warped current sheet, produce stochastic orbit perturbations. From this a diffusive description of particle motion can be derived, provided the dust particles are sufficiently small. The effects of large unipolar magnetic field regions at high heliographic latitudes will be briefly discussed.

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