scholarly journals A statistical comparison of hot-ion properties at geosynchronous orbit during intense and moderate geomagnetic storms at solar maximum and minimum

2006 ◽  
Vol 111 (A7) ◽  
Author(s):  
Jichun Zhang ◽  
Michael W. Liemohn ◽  
Michelle F. Thomsen ◽  
Janet U. Kozyra ◽  
Michael H. Denton ◽  
...  
Keyword(s):  
Geomagnetic Storms ◽  
Solar Maximum ◽  
Geosynchronous Orbit ◽  
Statistical Comparison

Flux dropouts of plasma and energetic particles at geosynchronous orbit during large geomagnetic storms: Entry into the lobes

1995 ◽  
Vol 100 (A5) ◽  
pp. 8031 ◽  
Author(s):  
Mark B. Moldwin ◽  
Michelle F. Thomsen ◽  
Samuel J. Bame ◽  
David J. McComas ◽  
Joachim Birn ◽  
...  
Keyword(s):  
Geomagnetic Storms ◽  
Energetic Particles ◽  
Geosynchronous Orbit

scholarly journals Formation of a strong southward IMF near the solar maximum of cycle 23

2004 ◽  
Vol 22 (2) ◽  
pp. 673-687 ◽  
Author(s):  
S. Watari ◽  
M. Vandas ◽  
T. Watanabe
Keyword(s):  
Solar Wind ◽  
Magnetic Fields ◽  
Geomagnetic Storms ◽  
Solar Maximum ◽  
Interplanetary Shocks ◽  
Physical Processes ◽  
Interplanetary Magnetic Fields ◽  
Interplanetary Physics ◽  
Solar Wind Parameters ◽  
Interplanetary Disturbance

Abstract. We analyzed observations of the solar activities and the solar wind parameters associated with large geomagnetic storms near the maximum of solar cycle 23. This analysis showed that strong southward interplanetary magnetic fields (IMFs), formed through interaction between an interplanetary disturbance, and background solar wind or between interplanetary disturbances are an important factor in the occurrence of intense geomagnetic storms. Based on our analysis, we seek to improve our understanding of the physical processes in which large negative Bz's are created which will lead to improving predictions of space weather. Key words. Interplanetary physics (Flare and stream dynamics; Interplanetary magnetic fields; Interplanetary shocks)

scholarly journals Solar cycle effect on geomagnetic storms caused by interplanetary magnetic clouds

2006 ◽  
Vol 24 (12) ◽  
pp. 3383-3389 ◽  
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.

The causes of geomagnetic storms during solar maximum

Eos ◽  
1994 ◽  
Vol 75 (5) ◽  
pp. 49 ◽  
Author(s):  
Bruce T. Tsurutani ◽  
Walter D. Gonzalez
Keyword(s):  
Geomagnetic Storms ◽  
Solar Maximum

scholarly journals Carrington Longitudinal and Solar Cycle Distribution of the Super Active Regions From 1976 to 2018

2021 ◽  
Author(s):  
MIng-Xian Zhao ◽  
Guiming Le ◽  
Yonghua Liu ◽  
Tian Mao
Keyword(s):  
Solar Cycle ◽  
Space Weather ◽  
Geomagnetic Storms ◽  
Solar Maximum ◽  
Active Regions ◽  
Ground Level ◽  
Weather Events ◽  
Flare Index ◽  
Statistical Results ◽  
Extreme Space Weather Events

Abstract We studied the Carrington longitudinal and solar cycle distribution of the super active regions (SARs) from 1976to 2018. There were 51 SARs during this period. We divided the SARs into SARs1 and SARs2. SARs1 refers tothe SARs that produced extreme space weather events including ≥X5.0 flares, ground level events (GLEs) andsuper geomagnetic storms (SGSs: Dst≤ −250 nT), while SARs2 did not produce extreme space weather events.The total number of SARs1 and SARs2 are 32 and 19, respectively. The statistical results show that 34.4%, 65.6%and 78.1% of the SARs1 appeared in the ascending phase, descending phase and in the period from two yearsbefore to the three years after the solar maximum, respectively, while 52.6%, 47.4% and 100% of the SARs2appeared in the ascending phase, descending phase and in the period from two years before to the three years aftersolar maximum, respectively. The Carrington longitude distribution of the SARs1 shows that SARs1 in thelongitudinal scope of [0,150°] produced ≥X5.0 flares and GLEs, while only the SARs1 in the longitude range of[150°,360°] not only produced ≥X5.0 flares and GLEs, but also produced SGSs. The total number of SARsduring a SC has a good correlation with the SC size. However, the largest flare index of a SAR within a SC has apoor correlation with the SC size, implying that the number of SARs in a weak SC will be small. However, aweak SC may have a SAR that can produce very strong solar flare activities.

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

2006 ◽  
Vol 111 (A1) ◽  
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

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

1997 ◽  
Vol 15 (10) ◽  
pp. 1265-1270 ◽  
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.

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