MHD‐test particles simulations of moderate CME and CIR‐driven geomagnetic storms at solar minimum

Mid-term prognoses of geomagnetic storms require an improvement since the&#1091; are known to have rather low accuracy which does not exceed 40% in solar minimum. We claim that the problem lies in the approach. Current mid-term forecasts are typically built using the same paradigm as short-term ones and suggest an analysis of the solar wind conditions typical for geomagnetic storms. According to this approach, there is a 20-60 minute delay between the arrival of a geoeffective flow/stream to L1 and the arrival of the signal from the spacecraft to Earth, which gives a necessary advance time for a short-term prognosis. For the mid-term forecast with an advance time from 3 hours to 3 days, this is not enough. Therefore, we have suggested finding precursors of geomagnetic storms observed in the solar wind. Such precursors are variations in the solar wind density and the interplanetary magnetic field in the ULF range associated with crossings of magnetic cavities in front of the arriving geoeffective high-speed streams and flows (Khabarova et al., 2015, 2016, 2018; Adhikari et al., 2019). Despite some preliminary studies have shown that this might be a perspective way to create a mid-term prognosis (Khabarova 2007; Khabarova & Yermolaev, 2007), the problem of automatization of the prognosis remained unsolved.

Download Full-text

The response of the H geocorona between 3 and 8 Re to geomagnetic disturbances studied using TWINS stereo Lyman-α data

Annales Geophysicae ◽

10.5194/angeo-35-171-2017 ◽

2017 ◽

Vol 35 (1) ◽

pp. 171-179 ◽

Cited By ~ 17

Author(s):

Jochen H. Zoennchen ◽

Uwe Nass ◽

Hans J. Fahr ◽

Jerry Goldstein

Keyword(s):

Solar Minimum ◽

Column Density ◽

Geomagnetic Storms ◽

Neutral Hydrogen ◽

Wind Pressure ◽

Time Shift ◽

Line Center ◽

Storm Event ◽

Geomagnetic Disturbances ◽

Pressure Peak

Abstract. Circumterrestrial Lyman-α column brightness observations from 3–8 Earth radii (Re) have been used to study temporal density variations in the exospheric neutral hydrogen as response to geomagnetic disturbances of different strength, i.e., Dst peak values between −26 and −147 nT. The data used were measured by the two Lyman-α detectors (LAD1/2) onboard both TWINS satellites between the solar minimum of 2008 and near the solar maximum of 2013. The solar Lyman-α flux at 121.6 nm is resonantly scattered near line center by exospheric H atoms and measured by the TWINS LADs. Along a line of sight (LOS), the scattered LOS-column intensity is proportional to the LOS H column density, assuming optically thin conditions above 3 Re. In the case of the eight analyzed geomagnetic storms we found a significant increase in the exospheric Lyman-α flux between 9 and 23 % (equal to the same increase in H column density ΔnH) compared to the undisturbed case short before the storm event. Even weak geomagnetic storms (e.g., Dst peak values ≥  −41 nT) under solar minimum conditions show increases up to 23 % of the exospheric H densities. The strong H density increase in the observed outer exosphere is also a sign of an enhanced H escape flux during storms. For the majority of the storms we found an average time shift of about 11 h between the time when the first significant dynamic solar wind pressure peak (pSW) hits the Earth and the time when the exospheric Lyman-α flux variation reaches its maximum. The results show that the (relative) exospheric density reaction of ΔnH have a tendency to decrease with increasing peak values of Dst index or the Kp index daily sum. Nevertheless, a simple linear correlation between ΔnH and these two geomagnetic indices does not seem to exist. In contrast, when recovering from the peak back to the undisturbed case, the Kp index daily sum and the ΔnH essentially show the same temporal recovery.

Download Full-text

On the variations of the thermospheric structure

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1965.0236 ◽

1965 ◽

Vol 288 (1415) ◽

pp. 493-509 ◽

Cited By ~ 6

Keyword(s):

Solar Activity ◽

Solar Cycle ◽

Phase Shift ◽

Diurnal Variation ◽

Solar Minimum ◽

Geomagnetic Storms ◽

Atmospheric Temperature ◽

Atmospheric Density ◽

Height Range ◽

Atmospheric Variations

The paper discusses the properties of the different effects which have been found to occur in the thermosphere and some conclusions which can be drawn with regard to the physics of the thermosphere. In the discussion of the diurnal variation the emphasis is on the behaviour of the diurnal amplitude in density during the solar cycle. At the height range between 200 and 300 km the amplitude has remarkably increased with decreasing solar activity. The relation between atmospheric density and temperature and the solar e.u.v. flux and the solar 10.7 cm flux—the latter serving as a convenient parameter—is discussed. The observational results for a phaseshift between the variations in the e.u.v. flux (or 10.7 cm flux) and the correlated variations in atmospheric temperature (or density) lie in the range between 0.5 and 2.3 days. During the solar minimum the atmospheric variations which parallel the 10.7 cm flux are far less pronounced than the variations correlated with geomagnetic activity. The phase shift derived from 45 geomagnetic storms and correlated density changes has been found to be 6 ± 3 (m.e.) h.

Download Full-text

Solar cycle effect on geomagnetic storms caused by interplanetary magnetic clouds

Annales Geophysicae ◽

10.5194/angeo-24-3383-2006 ◽

2006 ◽

Vol 24 (12) ◽

pp. 3383-3389 ◽

Cited By ~ 12

Author(s):

C.-C. Wu ◽

R. P. Lepping

Keyword(s):

Solar Wind ◽

Geomagnetic Storm ◽

Solar Minimum ◽

Geomagnetic Storms ◽

Solar Maximum ◽

Solar Wind Speed ◽

Magnetic Clouds ◽

Active Period ◽

Quiet Period ◽

Solar Wind Parameters

Abstract. We investigated geomagnetic activity which was induced by interplanetary magnetic clouds during the past four solar cycles, 1965–1998. We have found that the intensity of such geomagnetic storms is more severe in solar maximum than in solar minimum. In addition, we affirm that the average solar wind speed of magnetic clouds is faster in solar maximum than in solar minimum. In this study, we find that solar activity level plays a major role on the intensity of geomagnetic storms. In particular, some new statistical results are found and listed as follows. (1) The intensity of a geomagnetic storm in a solar active period is stronger than in a solar quiet period. (2) The magnitude of negative Bzmin is larger in a solar active period than in a quiet period. (3) Solar wind speed in an active period is faster than in a quiet period. (4) VBsmax in an active period is much larger than in a quiet period. (5) Solar wind parameters, Bzmin, Vmax and VBsmax are correlated well with geomagnetic storm intensity, Dstmin during a solar active period. (6) Solar wind parameters, Bzmin, and VBsmax are not correlated well (very poorly for Vmax) with geomagnetic storm intensity during a solar quiet period. (7) The speed of the solar wind plays a key role in the correlation of solar wind parameters vs. the intensity of a geomagnetic storm. (8) More severe storms with Dstmin≤−100 nT caused by MCs occurred in the solar active period than in the solar quiet period.

Download Full-text

Fe/O ratio behavior as an indicator of solar plasma state at different solar activity manifestations and in periods of their absence

Solnechno-Zemnaya Fizika ◽

10.12737/szf-41201804 ◽

2018 ◽

pp. 33-58

Author(s):

Геннадий Минасянц ◽

Gennady Minasyants ◽

Тамара Минасянц ◽

Tamara Minasyants ◽

Владимир Томозов ◽

...

Keyword(s):

Solar Wind ◽

Solar Activity ◽

Cosmic Rays ◽

Ionization Potential ◽

Solar Minimum ◽

Geomagnetic Storms ◽

Galactic Cosmic Rays ◽

Ion Fluxes ◽

Ion Energy ◽

First Ionization Potential

We report the results of the investigation into plasma physical characteristics at various solar activity manifestations and in periods of their absence. These results have been obtained from quantitative estimates of the relative abundance of Fe/O ions in different energy ranges. Maximum values of the Fe/O ratio is shown to correspond to particle fluxes from impulsive flares for ions with energies <2 MeV/n (the most significant manifestation of the FIP effect). In particle fluxes from gradual flares, the Fe/O value decreases smoothly with ion energy and is noticeably inferior to values of fluxes in impulsive events. We have established that the properties of flares of solar cosmic rays indicate their belonging to a separate subclass in the total population of gradual events. Relying on variations in the abundance of Fe/O ions, we propose an xplanation of the solar plasma behavior during the development of flares of both classes. Magnetic clouds (a separate type of coronal mass ejections (CME)), which have regions of turbulent compression and are sources of strong geomagnetic storms, exhibit a relative composition of Fe ions comparable to the abundance of Fe in ion fluxes from gradual flares. We have found out that the Fe/O value can be used to detect penetration of energetic flare plasma into the CME body at the initial phase of their joint development and to estimate its relative contribution. During solar minimum with complete absence of sunspots, the Fe/O ratio during periods of “quiet” solar wind show absolutely low values of Fe/O=0.004–0.010 in the energy range from 2–5 to 30 MeV/n. This is associated with the manifestation of the cosmic ray anomalous component, which causes an increase in the intensity of ion fluxes with a high first ionization potential, including oxygen (O), and elements with a low first ionization potential (Fe) demonstrate weakening of the fluxes. As for particles with higher energies (Ek>30 MeV/n), the Fe/O increase is due to the decisive influence of galactic cosmic rays on the composition of impurity elements in the solar wind under solar minimum conditions. The relative content of heavy elements in galactic cosmic rays 30–500 MeV/n is similar to values in fluxes from gradual flares during high solar activity. During solar minimum without sunspots, the behavior of Fe/O for different ion energy ranges in plasma flows from coronal holes (CH) and in the solar wind exhibits only minor deviations. At the same time, plasma flows associated with the disturbed frontal CH region can be sources of moderate geomagnetic storms.

Download Full-text

Fe/O ratio behavior as an indicator of solar plasma state at different solar activity manifestations and in periods of their absence

Solar-Terrestrial Physics ◽

10.12737/stp-41201804 ◽

2018 ◽

Vol 4 (1) ◽

pp. 29-50

Author(s):

Геннадий Минасянц ◽

Gennady Minasyants ◽

Тамара Минасянц ◽

Tamara Minasyants ◽

Владимир Томозов ◽

...

Keyword(s):

Solar Wind ◽

Solar Activity ◽

Cosmic Rays ◽

Ionization Potential ◽

Solar Minimum ◽

Geomagnetic Storms ◽

Galactic Cosmic Rays ◽

Ion Fluxes ◽

Ion Energy ◽

First Ionization Potential

We report the results of the investigation into plasma physical characteristics at various solar activity manifestations and in periods of their absence. These results have been obtained from quantitative estimates of the relative abundance of Fe/O ions in different energy ranges. Maximum values of the Fe/O ratio is shown to correspond to particle fluxes from impulsive flares for ions with energies <2 MeV/n (the most significant manifestation of the FIP effect). In particle fluxes from gradual flares, the Fe/O value decreases smoothly with ion energy and is noticeably inferior to values of fluxes in impulsive events. We have established that the properties of flares of solar cosmic rays indicate their belonging to a separate subclass in the total population of gradual events. Relying on variations in the abundance of Fe/O ions, we propose an xplanation of the solar plasma behavior during the development of flares of both classes. Magnetic clouds (a separate type of coronal mass ejections (CME)), which have regions of turbulent compression and are sources of strong geomagnetic storms, exhibit a relative composition of Fe ions comparable to the abundance of Fe in ion fluxes from gradual flares. We have found out that the Fe/O value can be used to detect penetration of energetic flare plasma into the CME body at the initial phase of their joint development and to estimate its relative contribution. During solar minimum with complete absence of sunspots, the Fe/O ratio during periods of “quiet” solar wind show absolutely low values of Fe/O=0.004–0.010 in the energy range from 2–5 to 30 MeV/n. This is associated with the manifestation of the cosmic ray anomalous component, which causes an increase in the intensity of ion fluxes with a high first ionization potential, including oxygen (O), and elements with a low first ionization potential (Fe) demonstrate weakening of the fluxes. As for particles with higher energies (Ek>30 MeV/n), the Fe/O increase is due to the decisive influence of galactic cosmic rays on the composition of impurity elements in the solar wind under solar minimum conditions. The relative content of heavy elements in galactic cosmic rays 30–500 MeV/n is similar to values in fluxes from gradual flares during high solar activity. During solar minimum without sunspots, the behavior of Fe/O for different ion energy ranges in plasma flows from coronal holes (CH) and in the solar wind exhibits only minor deviations. At the same time, plasma flows associated with the disturbed frontal CH region can be sources of moderate geomagnetic storms.

Download Full-text

A statistical comparison of solar wind sources of moderate and intense geomagnetic storms at solar minimum and maximum

Journal of Geophysical Research Atmospheres ◽

10.1029/2005ja011065 ◽

2006 ◽

Vol 111 (A1) ◽

Cited By ~ 30

Author(s):

Jichun Zhang ◽

Michael W. Liemohn ◽

Janet U. Kozyra ◽

Michelle F. Thomsen ◽

Heather A. Elliott ◽

...

Keyword(s):

Solar Wind ◽

Solar Minimum ◽

Geomagnetic Storms ◽

Statistical Comparison ◽

Solar Wind Sources

Download Full-text

Relationships between the AE, ap and Dst indices near solar minimum (1974) and at solar maximum (1979)

Annales Geophysicae ◽

10.1007/s00585-997-1265-x ◽

1997 ◽

Vol 15 (10) ◽

pp. 1265-1270 ◽

Cited By ~ 27

Author(s):

M. M. Fares Saba ◽

W. D. Gonzalez ◽

A. L. Clúa de Gonzalez

Keyword(s):

Seasonal Variation ◽

Solar Minimum ◽

Ring Current ◽

Geomagnetic Storms ◽

Solar Maximum ◽

Correlation Coefficients ◽

The Sun ◽

Yearly Average ◽

First Time ◽

Activity Indices

Abstract. Three-hourly average values of the Dst, AE and ap geomagnetic activity indices have been studied for 1 year's duration near the solar minimum (1974) and also at the solar maximum (1979). In 1979 seven intense geomagnetic storms (Dst <–100 nT) occurred, whereas in 1974 only three were reported. This study reveals: (1) the yearly average of AE is greater in 1974 than in 1979, whereas the inverse seems to be true for the yearly average of Dst, when a higher number of intense storms is present. These averages indicate the kind of activity occurring on the sun as shown in earlier work. (2) The seasonal variation of Dst is higher than that of ap and is almost negligible in AE. (3) The correlation coefficient of ap × AE is in general the highest, as the magnetometers that monitor both indices are close, and is surpassed only by the ap × Dst correlation during geomagnetic storms, when the influence of the ring current is dominant. The correlation of ap × Dst also shows a seasonal variability. (4) For the first time a study of correlation between ap and a linear combination of AE and Dst has also been made. We found higher correlation coefficients in this case as compared to those between ap × Dst and ap × AE.

Download Full-text

Sources of geomagnetic storms for solar minimum and maximum conditions during 1972-2000

Geophysical Research Letters ◽

10.1029/2001gl013052 ◽

2001 ◽

Vol 28 (13) ◽

pp. 2569-2572 ◽

Cited By ~ 140

Author(s):

I. G. Richardson ◽

E. W. Cliver ◽

H. V. Cane

Keyword(s):

Solar Minimum ◽

Geomagnetic Storms

Download Full-text

MHD‐test particles simulations of moderate CME and CIR‐driven geomagnetic storms at solar minimum