Coronal shocks associated with CMEs and flares and their space weather consequences

AbstractWe study the geoeffectiveness of a sample of complex events; each includes a coronal type II burst, accompanied by a GOES SXR flare and LASCO CME. The radio bursts were recorded by the ARTEMIS-IV radio spectrograph, in the 100-650 MHz range; the GOES SXR flares and SOHO/LASCO CMEs, were obtained from the Solar Geophysical Data (SGD) and the LASCO catalogue respectively. These are compared with changes of solar wind parameters and geomagnetic indices in order to establish a relationship between solar energetic events and their effects on geomagnetic activity.

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Seasonal and diurnal variations of geomagnetic activity and their role in Space Weather forecast

Canadian Journal of Physics ◽

10.1139/p01-049 ◽

2001 ◽

Vol 79 (6) ◽

pp. 907-920 ◽

Cited By ~ 6

Author(s):

W Lyatsky ◽

A M Hamza

Keyword(s):

Solar Wind ◽

Seasonal Variation ◽

Diurnal Variation ◽

Geomagnetic Activity ◽

Space Weather ◽

Weather Forecast ◽

Diurnal Variations ◽

Ionospheric Conductivity ◽

Solar Wind Parameters ◽

Possible Cause

A possible test for different models explaining the seasonal variation in geomagnetic activity is the diurnal variation. We computed diurnal variations both in the occurrence of large AE (auroral electrojet) indices and in the AO index. (AO is the auroral electrojet index that provides a measure of the equivalent zonal current.) Both methods show a similar diurnal variation in geomagnetic activity with a deep minimum around (37) UT (universal time) in winter and a shallower minimum near 59 UT in equinoctial months. The observed UT variation is consistent with the results of other scientists, but it is different from that expected from the RussellMcPherron mechanism proposed to explain the seasonal variation. It is suggested that the possible cause for the diurnal and seasonal variations may be variations in nightside ionospheric conductivity. Recent experimental results show an important role for ionospheric conductivity in particle acceleration and geomagnetic disturbance generation. They also show that low ionospheric conductivity is favorable to the generation of auroral and geomagnetic activity. The conductivity in conjugate nightside auroral zones (where substorm generation takes place) is minimum at equinoxes, when both auroral zones are in darkness. The low ionospheric conductivity at equinoxes may be a possible cause for the seasonal variation in the geomagnetic activity with maxima in equinoctial months. The diurnal variation in geomagnetic activity can be produced by the UT variation in the nightside ionospheric conductivity, which in winter and at equinoxes has a maximum around 45 UT that may lead to a minimum in geomagnetic activity at this time. We calculated the correlation patterns for the AE index versus solar-wind parameters inside and outside the (27) UT sector related to the minimum in geomagnetic activity. The correlation patterns appear different in these two sectors indeed, which is well consistent with the UT variation in geomagnetic activity. It also shows that it is possible to improve significantly the reliability of the Space Weather forecast by taking into account the dependence of geomagnetic activity not only on solar-wind parameters but also on UT and season. Our test shows that a simple account for the dependence of geomagnetic activity on UT can improve the reliability of the Space Weather forecast by at least 50% in the 27 UT sector in winter and equinoctial months. PACS No.: 91.25Le

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Is Our Understanding of Solar-Wind/Magnetosphere Coupling Satisfactory?

Frontiers in Astronomy and Space Sciences ◽

10.3389/fspas.2021.634073 ◽

2021 ◽

Vol 8 ◽

Author(s):

Joseph E. Borovsky

Keyword(s):

Solar Wind ◽

Geomagnetic Activity ◽

Space Weather ◽

Unsolved Problem ◽

Solar Wind Plasma ◽

Space Physics ◽

Geomagnetic Indices ◽

Ionosphere Model ◽

Fundamental Understanding ◽

Full Knowledge

An assessment of our physics-based understanding of solar-wind/magnetosphere coupling finds that the understanding is not complete. Solar-wind/magnetosphere coupling is foundational to magnetospheric physics and it is a key to comprehending and predicting space weather. We are modestly successful at correlating solar-wind variables with geomagnetic indices, but we lack the full knowledge to describe in detail how the shocked solar-wind plasma transports mass, momentum, and energy into the magnetosphere-ionosphere system and how the shocked solar wind drives geomagnetic activity and magnetospheric evolution. The controlling solar-wind factors that govern the driving of the magnetosphere-ionosphere system are not accurately known. Without this knowledge accurate predictions of the magnetospheric behavior cannot be made and no magnetosphere-ionosphere model will work correctly if it is driven incorrectly. Further, without a fundamental understanding, the prediction of the system reaction to some as-yet-unseen extreme solar-wind conditions will not be possible. In this perspective article several gaps in our knowledge are cataloged. The deficiencies in our physical understanding of solar-wind/magnetosphere coupling constitute a major unsolved problem for space physics (and for astrophysics), a problem that demands enhanced, coordinated research.

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Relation between coronal type II bursts, associated flares and CMEs

Proceedings of the International Astronomical Union ◽

10.1017/s1743921309029457 ◽

2008 ◽

Vol 4 (S257) ◽

pp. 299-301 ◽

Cited By ~ 1

Author(s):

George Pothitakis ◽

Panagiota Preka-Papadema ◽

Xenophon Moussas ◽

Constantine Caroubalos ◽

Constantine Alissandrakis ◽

...

Keyword(s):

Blast Wave ◽

Radio Burst ◽

Geophysical Data ◽

Radio Bursts ◽

Type Ii ◽

Complex Events ◽

Type Ii Bursts

AbstractWe study a sample of complex events; each includes a coronal type II burst, accompanied by a GOES SXR flare and LASCO CME. The radio bursts were recorded by the ARTEMIS-IV radio spectrograph (100-650 MHz range); the GOES SXR flares and SOHO/LASCO CMEs, were obtained from the Solar Geophysical Data (SGD) and the LASCO lists respectively. The radio burst-flare-CME characteristics were compared and two groups of events with similar behavior were isolated. In the first the type II shock exciter appears to be a flare blast wave propagating in the wake of a CME. In the second the type II burst appears CME initiated though it is not always clear if it is driven by the bow or the flanks of the CME or if it is a reconnection shock.

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Shock-wave Radio Probing of Solar Wind Sources in Coronal Magnetic Fields

The Astrophysical Journal ◽

10.3847/1538-4357/ac2f3f ◽

2021 ◽

Vol 923 (2) ◽

pp. 255

Author(s):

Artem Koval ◽

Marian Karlický ◽

Aleksander Stanislavsky ◽

Bing Wang ◽

Miroslav Bárta ◽

...

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Magnetic Fields ◽

Space Weather ◽

Radio Bursts ◽

Type Ii ◽

Modeling And Forecasting ◽

Type Ii Radio Bursts ◽

Corona Structure ◽

Solar Wind Sources

Abstract The space weather effects in the near-Earth environment as well as in atmospheres of other terrestrial planets arise by corpuscular radiation from the Sun, known as the solar wind. The solar magnetic fields govern the solar corona structure. Magnetic-field strength values in the solar wind sources—key information for modeling and forecasting the space weather climate—are derived from various solar space- and ground-based observations, but so far not accounting for specific types of radio bursts. These are “fractured” type II radio bursts attributed to collisions of shock waves with coronal structures emitting the solar wind. Here, we report on radio observations of two “fractured” type II bursts to demonstrate a novel tool for probing of magnetic-field variations in the solar wind sources. These results have a direct impact on interpretations of this class of bursts and contribute to the current studies of the solar wind emitters.

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ASSOCIATION BETWEEN VARIATIONS OF SOLAR WIND PARAMETERS AND GEOMAGNETIC ACTIVITY INDEX Ap IN 2003 - 2005

Radio Physics and Radio Astronomy ◽

10.1615/radiophysicsradioastronomy.v2.i3.20 ◽

2011 ◽

Vol 2 (3) ◽

pp. 205-210 ◽

Cited By ~ 2

Author(s):

Igor Savel'evich Fal'kovich ◽

M. R. Olyak ◽

Nikolai Nikolaevich Kalinichenko ◽

I. N. Bubnov

Keyword(s):

Solar Wind ◽

Geomagnetic Activity ◽

Activity Index ◽

Solar Wind Parameters ◽

Geomagnetic Activity Index

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Wavelet Analysis on Solar Wind Parameters and Geomagnetic Indices

Solar Physics ◽

10.1007/s11207-012-0078-6 ◽

2012 ◽

Vol 280 (2) ◽

pp. 623-640 ◽

Cited By ~ 41

Author(s):

C. Katsavrias ◽

P. Preka-Papadema ◽

X. Moussas

Keyword(s):

Solar Wind ◽

Wavelet Analysis ◽

Geomagnetic Indices ◽

Solar Wind Parameters

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Physical meaning of the equinoctial effect for semi-annual variation in geomagnetic activity

Annales Geophysicae ◽

10.5194/angeo-27-1909-2009 ◽

2009 ◽

Vol 27 (5) ◽

pp. 1909-1914 ◽

Cited By ~ 4

Author(s):

A. Yoshida

Keyword(s):

Solar Wind ◽

Wind Velocity ◽

Geomagnetic Activity ◽

Physical Meaning ◽

Solar Wind Velocity ◽

Annual Variation ◽

Geomagnetic Disturbance ◽

Data Sets ◽

Key Factor ◽

Solar Wind Parameters

Abstract. Physical meaning of the equinoctial effect for semi-annual variation in geomagnetic activity is investigated based on the three-hourly am index and solar wind parameters. When the z component of the interplanetary magnetic field (IMF) in geocentric solar magnetospheric (GSM) coordinates is southward, am indices are well correlated with BsVx2, where Bs is the southward component of the IMF and Vx is the solar wind velocity in the sun-earth direction. The am-BsVx2 relationship, however, depends on the range of Vx2: the am in higher ranges of Vx2 tends to be larger than am in lower ranges of Vx2 for the same value of BsVx2 for both equinoctial and solstitial epochs. Using the data sets of the same Vx2 range, it is shown that distribution of points in the am-BsVx2 diagram at the solstitial epochs overlaps with that at the equinoctial epochs and the average am values in each BsVx2 bin in solstitial epochs are closely consistent with those in equinoctial epochs, if Vx2 for each point at solstices are reduced to Vx2sin2 (Ψ) where Ψ is the geomagnetic colatitude of the sub-solar point. Further, it is shown that monthly averages of the am index in the long period is well correlated with the values of sin2(ψ) for the middle day of each month. These findings indicate that the factor that contributes to the generation of geomagnetic disturbance is not the velocity of the solar wind, but the component of the solar wind velocity perpendicular to the dipole axis of the geomagnetic field. The magnitude of the perpendicular velocity component varies semi-annually even if the solar wind velocity remains constant, which is considered to be the long-missed key factor causing the equinoctial effect.

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Statistical analysis of solar wind parameters and geomagnetic indices during HILDCAA/HILDCAA ∗ occurrences between 1998 and 2007

Advances in Space Research ◽

10.1016/j.asr.2017.06.023 ◽

2017 ◽

Vol 60 (8) ◽

pp. 1850-1865 ◽

Cited By ~ 9

Author(s):

Alan Prestes ◽

Virginia Klausner ◽

Arian Ojeda González ◽

Silvio Leite Serra

Keyword(s):

Solar Wind ◽

Statistical Analysis ◽

Geomagnetic Indices ◽

Solar Wind Parameters

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Extremely low geomagnetic activity during the recent deep solar cycle minimum

Proceedings of the International Astronomical Union ◽

10.1017/s174392131200484x ◽

2011 ◽

Vol 7 (S286) ◽

pp. 200-209 ◽

Cited By ~ 12

Author(s):

E. Echer ◽

B. T. Tsurutani ◽

W. D. Gonzalez

Keyword(s):

Solar Wind ◽

Solar Cycle ◽

Geomagnetic Activity ◽

Solar Minimum ◽

Solar Wind Speed ◽

Sunspot Cycle ◽

Cycle Minimum ◽

Current Minimum ◽

Solar Wind Parameters ◽

Xix Century

AbstractThe recent solar minimum (2008-2009) was extreme in several aspects: the sunspot number, Rz, interplanetary magnetic field (IMF) magnitude Bo and solar wind speed Vsw were the lowest during the space era. Furthermore, the variance of the IMF southward Bz component was low. As a consequence of these exceedingly low solar wind parameters, there was a minimum in the energy transfer from solar wind to the magnetosphere, and the geomagnetic activity ap index reached extremely low levels. The minimum in geomagnetic activity was delayed in relation to sunspot cycle minimum. We compare the solar wind and geomagnetic activity observed in this recent minimum with previous solar cycle values during the space era (1964-2010). Moreover, the geomagnetic activity conditions during the current minimum are compared with long term variability during the period of available geomagnetic observations. The extremely low geomagnetic activity observed in this solar minimum was previously recorded only at the end of XIX century and at the beginning of the XX century, and this might be related to the Gleissberg (80-100 years) solar cycle.

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