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).

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 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.

Investigation of the coronal heating through phase relation of solar activity indexes

2020 ◽  
Vol 37 ◽  
Author(s):  
K. J. Li ◽  
J. C. Xu ◽  
Z. Q. Yin ◽  
J. L. Xie ◽  
W. Feng
Keyword(s):  
Solar Wind ◽  
Solar Activity ◽  
Phase Relation ◽  
Large Scale ◽  
Solar Rotation ◽  
Rotation Period ◽  
Magnetic Activity ◽  
Coronal Heating ◽  
Small Scale

Abstract The coronal heating problem is a long-standing perplexing issue. In this study, 13 solar activity indexes are used to investigate their phase relation with the sunspot number (SSN). Only three of them are found to statistically significantly lag the SSN (large-scale magnetic activity) by about one solar rotation period; the three indexes are total solar irradiance (TSI), the modified coronal index, and the solar wind velocity; the former two indexes may represent the long-term variation of energy quantity of the heated photosphere and corona, respectively. The Mount Wilson Sunspot Index (MWSI) and the Magnetic Plage Strength Index (MPSI), which reflect the large- and small-scale magnetic field activities, respectively, are also utilised to investigate their phase relations with the three indexes. The three indexes are found to be much more intimately related to MPSI than to MWSI, and MWSI statistically significantly leads TSI by about one rotation period. The heated corona is found to pulse perfectly in step with the small-scale magnetic activity rather than the large-scale magnetic activity; furthermore, combined with observations, our statistical evidence should thus attribute coronal heating firmly to small-scale magnetic activity phenomena, such as spicules, micro-flares, nano-flares, and others. The photosphere and the corona are synchronously heated, which should seemingly prefer magnetic reconnection heating to wave heating. In the long term, such a coronal heating way is inferred effective. Statistically, it is also small-scale magnetic activity phenomena that produce TSI enhancement. Coronal heating and solar wind acceleration are found to be synchronous, as standard models require.

New Results of the Baikal Experiment on Forecasting Effect of Macroscopic Nonlocal Correlations

2019 ◽  
pp. 56-72
Author(s):  
S.M Korotaev ◽  
N.M. Budnev ◽  
V.O. Serdyuk ◽  
Ye.O. Kiktenko ◽  
D.A. Orekhova
Keyword(s):  
Solar Activity ◽  
Active Layer ◽  
Large Scale ◽  
Forecast Accuracy ◽  
Random Component ◽  
Low Frequencies ◽  
Nonlocal Correlations ◽  
Sea Current ◽  
Local Impacts

The long-term deep-sea experiment on study of macroscopic quantum nonlocal correlations of natural large-scale random dissipative processes has been conducted in Lake Baikal since 2012. Correlations of the probe processes in detectors insulated from classical local impacts, between each other and with the large-scale source-processes are studied. These correlations are observed at extremely low frequencies and characterized by the large time shifts. The most important feature of random process nonlocal correlations is presence of a considerable advanced component in them. The dominant source is solar activity. At the same time, the correlations with macroturbulence in the Baikal active layer are revealed. The advanced nonlocal correlations can be applied to forecast the processes with big random component. A forecast series of macroturbulence sea current velocity variations in the active layer, which demonstrated forecast accuracy of the order of tenths of cm/s at an advance of the order of month, has been obtained by the latest experimental data. The possibility of using nonlocal correlations to forecast solar activity in advance of the order of the year has also been demonstrated.

scholarly journals Solar wind velocity at solar maximum: A search for latitudinal effects

2004 ◽  
Vol 22 (10) ◽  
pp. 3721-3727
Author(s):  
B. Bavassano ◽  
R. D'Amicis ◽  
R. Bruno
Keyword(s):  
Solar Wind ◽  
Wind Velocity ◽  
Large Scale ◽  
Solar Wind Velocity ◽  
Velocity Structure ◽  
Ecliptic Plane ◽  
Magnetic Polarity ◽  
Point Of View ◽  
Statistical Point ◽  
Activity Maximum

Abstract. Observations by Ulysses during its second out-of-ecliptic orbit have shown that near the solar activity maximum the solar wind appears as a highly variable flow at all heliolatitudes. In the present study Ulysses data from polar latitudes are compared to contemporary ACE data in the ecliptic plane to search for the presence of latitudinal effects in the large-scale structure of the solar wind velocity. The investigated period roughly covers the Sun's magnetic polarity reversal. The Ulysses-ACE comparison is performed through a multi-scale statistical analysis of the velocity fluctuations at scales from 1 to 64 days. The results indicate that, from a statistical point of view, the character of the wind velocity structure does not appear to change remarkably with latitude. It is likely that this result is characteristic of the particular phase of the solar magnetic cycle.

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 Spectrum of geomagnetic activity in the period range 5−60 days: possible lunar influences

1998 ◽  
Vol 16 (7) ◽  
pp. 804-811 ◽  
Author(s):  
J. Střeštík
Keyword(s):  
Solar Wind ◽  
Solar Activity ◽  
High Speed ◽  
Solar Rotation ◽  
Solar Wind Speed ◽  
Frequency Resolution ◽  
Solar Activity Minimum ◽  
Activity Maximum ◽  
Average Spectrum ◽  
Significant Difference

Abstract. The series of daily Ap-indices has been subdivided into pentades (1932–1936 etc.) and spectra with fine-frequency resolution have been calculated for the indices in each of these intervals. Daily sunspot numbers have been processed in the same way. The average spectrum from all spectra in the pentades, as well as the spectrum from the whole interval have been calculated, and significant peaks have been determined. There is a significant difference between the spectra in the pentades containing the solar activity minimum (1932–1936, 1942–1946 etc.) and those containing the solar activity maximum (1937–1941, 1947–1951 etc.). Most peaks can be interpreted as a response to solar rotation and to the structure of solar wind speed (two high-speed streams per solar rotation), both modulated by the 11-year, annual and semi-annual waves. No significant peak corresponding to the period of the synodic month, or its half has been found. This result suggests that the influence of lunar cycles on some natural phenomena (if any) is not mediated by geomagnetic activity.Key words. Geomagnetism and paleomagnetism · Time variations · Diurnal to secular · Magnetospheric physics · Solar wind-magnetosphere interactions

scholarly journals Long-term variations in the neutral gas composition of the termosphere above Irkutsk

2015 ◽  
Vol 1 (4) ◽  
pp. 30-34 ◽  
Author(s):  
Галина Кушнаренко ◽  
Galina Kushnarenko ◽  
Ольга Яковлева ◽  
Olga Yakovleva ◽  
Галина Кузнецова ◽  
...  
Keyword(s):  
Solar Activity ◽  
Gas Composition ◽  
Solar Activity Minimum ◽  
Ionospheric Layer ◽  
Neutral Gas ◽  
Different Seasons ◽  
Long Term Variations

Long-term variations of [O]/[N2] and [O2]/[O] ratios of dominant gas components of the thermosphere are analyzed for 2003–2013. The variations are estimated using the technique developed by the authors and Irkutsk (52° N, 104° E) digisonde data for heights lower than the ionospheric layer F1 maximum, quiet and disturbed geomagnetic conditions, and different seasons. For summer quiet and disturbed conditions, the [O2]/[O] ratio is found to be maximum during long solar activity minimum.

scholarly journals Three-Dimensional Simulations of Solar Wind Preconditioning and the 23 July 2012 Interplanetary Coronal Mass Ejection

Solar Physics ◽  
2020 ◽  
Vol 295 (9) ◽  
Author(s):  
Ravindra T. Desai ◽  
Han Zhang ◽  
Emma E. Davies ◽  
Julia E. Stawarz ◽  
Joan Mico-Gomez ◽  
...  
Keyword(s):  
Solar Wind ◽  
Coronal Mass Ejection ◽  
Large Scale ◽  
Weather Forecasting ◽  
Time Window ◽  
Initial Conditions ◽  
Interplanetary Space ◽  
Three Dimensional ◽  
Interplanetary Coronal Mass Ejection ◽  
Mass Ejection

Abstract Predicting the large-scale eruptions from the solar corona and their propagation through interplanetary space remains an outstanding challenge in solar- and helio-physics research. In this article, we describe three-dimensional magnetohydrodynamic simulations of the inner heliosphere leading up to and including the extreme interplanetary coronal mass ejection (ICME) of 23 July 2012, developed using the code PLUTO. The simulations are driven using the output of coronal models for Carrington rotations 2125 and 2126 and, given the uncertainties in the initial conditions, are able to reproduce an event of comparable magnitude to the 23 July ICME, with similar velocity and density profiles at 1 au. The launch time of this event is then varied with regards to an initial 19 July ICME and the effects of solar wind preconditioning are found to be significant for an event of this magnitude and to decrease over a time-window consistent with the ballistic refilling of the depleted heliospheric sector. These results indicate that the 23 July ICME was mostly unaffected by events prior, but would have traveled even faster had it erupted closer in time to the 19 July event where it would have experienced even lower drag forces. We discuss this systematic study of solar wind preconditioning in the context of space weather forecasting.

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