scholarly journals Sources of geomagnetic activity over the solar cycle: Relative importance of coronal mass ejections, high-speed streams, and slow solar wind

2000 ◽  
Vol 105 (A8) ◽  
pp. 18203-18213 ◽  
Author(s):  
I. G. Richardson ◽  
E. W. Cliver ◽  
H. V. Cane
Keyword(s):  
Solar Wind ◽  
Solar Cycle ◽  
Geomagnetic Activity ◽  
Coronal Mass Ejections ◽  
High Speed ◽  
Slow Solar Wind ◽  
Relative Importance

scholarly journals Solar wind high-speed streams and related geomagnetic activity in the declining phase of solar cycle 23

2011 ◽  
Vol 533 ◽  
pp. A49 ◽  
Author(s):  
G. Verbanac ◽  
B. Vršnak ◽  
S. Živković ◽  
T. Hojsak ◽  
A. M. Veronig ◽  
...  
Keyword(s):  
Solar Wind ◽  
Solar Cycle ◽  
Geomagnetic Activity ◽  
High Speed ◽  
Solar Cycle 23

scholarly journals Latitude dependence of long-term geomagnetic activity and its solar wind drivers

2015 ◽  
Vol 33 (5) ◽  
pp. 573-581 ◽  
Author(s):  
M. Myllys ◽  
N. Partamies ◽  
L. Juusola
Keyword(s):  
Solar Wind ◽  
Solar Cycle ◽  
Geomagnetic Activity ◽  
High Speed ◽  
Sunspot Cycle ◽  
Horizontal Magnetic Field ◽  
Geomagnetic Variations ◽  
Latitude Dependence ◽  
Latitude Region ◽  
The Impact

Abstract. To validate the usage of global indices in studies of geomagnetic activity, we have examined the latitude dependence of geomagnetic variations in Fennoscandia and Svalbard from 1994 to 2010. Daily standard deviation (SD) values of the horizontal magnetic field have been used as a measure of the ground magnetic disturbance level. We found that the timing of the geomagnetic minimum depends on the latitude region: corresponding to the minimum of sunspot cycle 22 (in 1996), the geomagnetic minimum occurred between the geomagnetic latitudes 57–61° in 1996 and at the latitudes 64–67° in 1997, which are the average auroral oval latitudes. During sunspot cycle 23, all latitude regions experienced the minimum in 2009, a year after the sunspot minimum. These timing differences are due to the latitude dependence of the 10 s daily SD on the different solar wind drivers. In the latitude region of 64–67°, the impact of the high-speed solar wind streams (HSSs) on the geomagnetic activity is the most pronounced compared to the other latitude groups, while in the latitude region of 57–61°, the importance of the coronal mass ejections (CMEs) dominates. The geomagnetic activity maxima during ascending solar cycle phases are typically caused by CME activity and occur especially in the oval and sub-auroral regions. The strongest geomagnetic activity occurs during the descending solar cycle phases due to a mixture of CME and HSS activity. Closer to the solar minimum, less severe geomagnetic activity is driven by HSSs and mainly visible in the poleward part of the auroral region. According to our study, however, the timing of the geomagnetic activity minima (and maxima) in different latitude bands is different, due to the relative importance of different solar wind drivers at different latitudes.

scholarly journals Extremely low geomagnetic activity during the recent deep solar cycle minimum

2011 ◽  
Vol 7 (S286) ◽  
pp. 200-209 ◽  
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.

A Catalogue of Coronal Mass Ejections Observed by the Heliospheric Imagers throughout the STEREO Mission

2020 ◽  
Author(s):  
David Barnes ◽  
Jackie Davies ◽  
Richard Harrison
Keyword(s):  
Solar Wind ◽  
Solar Cycle ◽  
Coronal Mass Ejections ◽  
Angular Separation ◽  
Propagation Direction ◽  
Wide Angle ◽  
Continuous Observation ◽  
Stereo Mission ◽  
Using Data ◽  
Kinematic Properties

<p>Understanding the evolution of the solar wind is fundamental to advancing our knowledge of energy and mass transport in the solar system, rendering it crucial to space weather and its prediction. The advent of truly wide-angle heliospheric imaging has revolutionised the study of Coronal Mass Ejections (CMEs) by enabling their direct and continuous observation out to 1 AU and beyond. A catalogue of CMEs has been compiled using data from the Heliospheric Imagers (HIs) on board the two STEREO spacecraft, which began as part of the FP7 HELCATS project. The mission was launched in 2006 and continues to provide data, therefore spanning 13 years, over which more than two-thousand CMEs have been observed using HI. To these CMEs, we apply geometric models that make use of both single-spacecraft and stereoscopic observations in order to determine their kinematic properties. These include CME speed, acceleration, propagation direction and launch time. The resulting kinematic properties and their statistics are discussed in the context of existing CME catalogues produced from coronagraph observations. This is done with emphasis on how the different models we apply influence our results and how these differences evolve over the solar cycle and as the angular separation of the STEREO spacecraft increases throughout the mission.</p>

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